Compact lidar design with high resolution and ultra-wide field of view

ABSTRACT

A compact LiDAR device is provided. The compact LiDAR device includes a first mirror disposed to receive one or more light beams and a polygon mirror optically coupled to the first mirror. The polygon mirror comprises a plurality of reflective facets. For at least two of the plurality of reflective facets, each reflective facet is arranged such that: a first edge, a second edge, and a third edge of the reflective facet correspond to a first line, a second line, and a third line; the first line and the second line intersect to form a first internal angle of a plane comprising the reflective facet; and the first line and the third line intersect to form a second internal angle of the plane comprising the reflective facet. The first internal angle is an acute angle; and the second internal angle is an obtuse angle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 63/178,467, filed Apr. 22, 2021, entitled “A COMPACT LIDARDESIGN WITH HIGH RESOLUTION AND ULTRAWIDE FIELD OF VIEW,” the content ofwhich is hereby incorporated by reference in its entirety for allpurposes.

FIELD OF THE TECHNOLOGY

This disclosure relates generally to optical scanning and, moreparticularly, to a compact LiDAR device configured to perform highresolution scanning of an ultra-wide field-of-view.

BACKGROUND

Light detection and ranging (LiDAR) systems use light pulses to createan image or point cloud of the external environment. Some typical LiDARsystems include a light source, a light transmitter, a light steeringsystem, and a light detector. The light source generates a light beamthat is directed by the light steering system in particular directionswhen being transmitted from the LiDAR system. When a transmitted lightbeam is scattered by an object, a portion of the scattered light returnsto the LiDAR system as a return light pulse. The light detector detectsthe return light pulse. Using the difference between the time that thereturn light pulse is detected and the time that a corresponding lightpulse in the light beam is transmitted, the LiDAR system can determinethe distance to the object using the speed of light. The light steeringsystem can direct light beams along different paths to allow the LiDARsystem to scan the surrounding environment and produce images or pointclouds. LiDAR systems can also use techniques other than time-of-flightand scanning to measure the surrounding environment.

SUMMARY

Embodiments of present disclosure are described below. In variousembodiments, a compact LiDAR device is provided. The compact LiDARdevice comprises a polygon mirror configured to scan an FOV in both thehorizontal and vertical directions, thereby achieving a very compactsize and an ultra-wide FOV. The polygon mirror comprises multiplereflective facets and at least some of the facets have non-90 degreetilt angles. The compact size of the LiDAR device enables the device tobe disposed inside many small spaces in a vehicle including, forexample, the headlight housing, the rear light housing, the rear-viewmirrors, the corners of the vehicle body, etc. In one example, thecompact LiDAR device can provide a horizontal FOV of about 120 degreesor more (about 240 degrees for using two such LiDAR devices) and avertical FOV of about 90 degrees or more. The compact LiDAR device canenable scanning multiple detection zones with different scanningresolutions. A higher scanning resolution is desirable in certainregions-of-interest (ROI) areas. Typical or lower scanning resolutionmay be used for scanning non-ROI areas. The compact LiDAR devicedisclosed herein can dynamically adjust the scanning of ROI areas andnon-ROI areas. Various embodiments of the compact LiDAR device aredescribed in more detail below.

In one embodiment, a compact LiDAR device is provided. The compact LiDARdevice includes a first mirror disposed to receive one or more lightbeams and a polygon mirror optically coupled to the first mirror. Thepolygon mirror comprises a plurality of reflective facets. For at leasttwo of the plurality of reflective facets, each reflective facet isarranged such that: a first edge, a second edge, and a third edge of thereflective facet correspond to a first line, a second line, and a thirdline; the first line and the second line intersect to form a firstinternal angle of a plane comprising the reflective facet; and the firstline and the third line intersect to form a second internal angle of theplane comprising the reflective facet. The first internal angle is anacute angle; and the second internal angle is an obtuse angle. Thecombination of the first mirror and the polygon mirror, when at leastthe polygon mirror is rotating, is configured to: steer the one or morelight beams both vertically and horizontally to illuminate an objectwithin a field-of-view, obtain return light formed based on the steeredone or more light beams illuminating the object within thefield-of-view, and redirect the return light to an optical receiverdisposed in the LiDAR scanning system.

In one embodiment, a light detection and ranging (LiDAR) scanning systemis provided. The LiDAR system includes a plurality of LiDAR devicesmountable to at least two of a left side, a front side, a front side,and a back side of a vehicle. Each of the plurality of LiDAR devicesincludes a first mirror disposed to receive one or more light beams anda polygon mirror optically coupled to the first mirror. The polygonmirror includes a plurality of reflective facets. For at least two ofthe plurality of reflective facets, each reflective facet is arrangedsuch that: a first edge, a second edge, and a third edge of thereflective facet corresponding to a first line, a second line, and athird line; the first line and the second line intersect to form a firstinternal angle of a plane comprising the reflective facet; and the firstline and the third line intersect to form a second internal angle of aplane comprising the reflective facet. The first internal angle of thereflective facet is an acute angle; and the second internal angle of therespective plane is an obtuse angle.

In one embodiment, a vehicle comprising a light detection and ranging(LiDAR) scanning system is provided. The LiDAR scanning system includesa plurality of LiDAR devices mountable to at least two of a left side, afront side, a front side, and a back side of a vehicle. Each of theplurality of LiDAR devices includes a first mirror disposed to receiveone or more light beams and a polygon mirror optically coupled to thefirst mirror. The polygon mirror includes a plurality of reflectivefacets. For at least two of the plurality of reflective facets, eachreflective facet is arranged such that: a first edge, a second edge, anda third edge of the reflective facet corresponding to a first line, asecond line, and a third line; the first line and the second lineintersect to form a first internal angle of a plane comprising thereflective facet; and the first line and the third line intersect toform a second internal angle of a plane comprising the reflective facet.The first internal angle of the reflective facet is an acute angle; andthe second internal angle of the respective plane is an obtuse angle.

In one embodiment, a method for scanning a field-of-view using a lightdetection and ranging (LiDAR) device is provided. The LiDAR devicecomprises a polygon mirror having a plurality of reflective facets. Themethod includes steering, by a first reflective facet of the pluralityof reflective facets of the polygon mirror, light to scan a first partof the field-of-view in a vertical direction. The first reflective facetis associated with an acute tilt angle. The method further comprisessteering, by a second reflective facet of the plurality of reflectivefacets of the polygon mirror, light to scan a second part of thefield-of-view in a vertical direction. The second reflective facet isassociated with an obtuse tilt angle. The method further includesgenerating scan lines corresponding to the first part of thefield-of-view in the vertical direction; and generating scan linescorresponding to the second part of the field-of-view in the verticaldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present application can be best understood by reference to thefigures described below taken in conjunction with the accompanyingdrawing figures, in which like parts may be referred to by likenumerals.

FIG. 1 illustrates one or more exemplary LiDAR systems disposed orincluded in a motor vehicle.

FIG. 2 is a block diagram illustrating interactions between an exemplaryLiDAR system and multiple other systems including a vehicle perceptionand planning system.

FIG. 3 is a block diagram illustrating an exemplary LiDAR system.

FIG. 4 is a block diagram illustrating an exemplary fiber-based lasersource.

FIGS. 5A-5C illustrate an exemplary LiDAR system using pulse signals tomeasure distances to objects disposed in a field-of-view (FOV).

FIG. 6 is a block diagram illustrating an exemplary apparatus used toimplement systems, apparatus, and methods in various embodiments.

FIG. 7A illustrates a simplified compact LiDAR device comprising apolygon mirror for steering light, according to some embodiments.

FIG. 7B illustrates a zoom-in view of the polygon mirror used in thecompact LiDAR device shown in FIG. 7A, according to some embodiments.

FIG. 8 illustrates a top view of a simplified LiDAR device enclosed in arear-view mirror assembly of a vehicle, according to some embodiments.

FIGS. 9A-9D illustrates several configurations of a polygon mirror,according to some embodiments.

FIG. 10 illustrates an example LiDAR scanning pattern using a compactLiDAR device disclosed herein, according to some embodiments.

FIG. 11A illustrates a top view of a rear-view mirror assembly and ahorizontal field-of-view (FOV) obtainable by a compact LiDAR deviceenclosed in the rear-view mirror assembly, according to someembodiments.

FIG. 11B illustrates a top view of a vehicle and the horizontal FOVs atthe two sides of the vehicle, according to some embodiments.

FIG. 11C illustrates a side view of a rear-view mirror assembly and avertical FOV obtainable by a compact LiDAR device enclosed in therear-view mirror assembly, according to some embodiments.

FIG. 11D illustrates a side view of a vehicle and the vertical FOV at aside of the vehicle, according to some embodiments.

FIG. 12 is a flowchart illustrating a method for scanning a FOV using acompact LiDAR device disclosed herein, according to some embodiments.

DETAILED DESCRIPTION

To provide a more thorough understanding of the present invention, thefollowing description sets forth numerous specific details, such asspecific configurations, parameters, examples, and the like. It shouldbe recognized, however, that such description is not intended as alimitation on the scope of the present invention but is intended toprovide a better description of the exemplary embodiments.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise:

The phrase “in one embodiment” as used herein does not necessarily referto the same embodiment, though it may. Thus, as described below, variousembodiments of the disclosure may be readily combined, without departingfrom the scope or spirit of the invention.

As used herein, the term “or” is an inclusive “or” operator and isequivalent to the term “and/or,” unless the context clearly dictatesotherwise.

The term “based on” is not exclusive and allows for being based onadditional factors not described unless the context clearly dictatesotherwise.

As used herein, and unless the context dictates otherwise, the term“coupled to” is intended to include both direct coupling (in which twoelements that are coupled to each other contact each other) and indirectcoupling (in which at least one additional element is located betweenthe two elements). Therefore, the terms “coupled to” and “coupled with”are used synonymously. Within the context of a networked environmentwhere two or more components or devices are able to exchange data, theterms “coupled to” and “coupled with” are also used to mean“communicatively coupled with”, possibly via one or more intermediarydevices.

Although the following description uses terms “first,” “second,” etc. todescribe various elements, these elements should not be limited by theterms. These terms are only used to distinguish one element fromanother. For example, a first edge could be termed a second edge and,similarly, a second edge could be termed a first edge, without departingfrom the scope of the various described examples. The first edge and thesecond edge can both be edges and, in some cases, can be separate anddifferent edges.

In addition, throughout the specification, the meaning of “a”, “an”, and“the” includes plural references, and the meaning of “in” includes “in”and “on”.

Although some of the various embodiments presented herein constitute asingle combination of inventive elements, it should be appreciated thatthe inventive subject matter is considered to include all possiblecombinations of the disclosed elements. As such, if one embodimentcomprises elements A, B, and C, and another embodiment compriseselements B and D, then the inventive subject matter is also consideredto include other remaining combinations of A, B, C, or D, even if notexplicitly discussed herein. Further, the transitional term “comprising”means to have as parts or members, or to be those parts or members. Asused herein, the transitional term “comprising” is inclusive oropen-ended and does not exclude additional, unrecited elements or methodsteps.

Throughout the following disclosure, numerous references may be maderegarding servers, services, interfaces, engines, modules, clients,peers, portals, platforms, or other systems formed from computingdevices. It should be appreciated that the use of such terms is deemedto represent one or more computing devices having at least one processor(e.g., ASIC, FPGA, PLD, DSP, x86, ARM, RISC-V, ColdFire, GPU, multi-coreprocessors, etc.) configured to execute software instructions stored ona computer readable tangible, non-transitory medium (e.g., hard drive,solid state drive, RAM, flash, ROM, etc.). For example, a server caninclude one or more computers operating as a web server, databaseserver, or other type of computer server in a manner to fulfilldescribed roles, responsibilities, or functions. One should furtherappreciate the disclosed computer-based algorithms, processes, methods,or other types of instruction sets can be embodied as a computer programproduct comprising a non-transitory, tangible computer readable mediumstoring the instructions that cause a processor to execute the disclosedsteps. The various servers, systems, databases, or interfaces canexchange data using standardized protocols or algorithms, possibly basedon HTTP, HTTPS, AES, public-private key exchanges, web service APIs,known financial transaction protocols, or other electronic informationexchanging methods. Data exchanges can be conducted over apacket-switched network, a circuit-switched network, the Internet, LAN,WAN, VPN, or other type of network.

As used in the description herein and throughout the claims that follow,when a system, engine, server, device, module, or other computingelement is described as being configured to perform or execute functionson data in a memory, the meaning of “configured to” or “programmed to”is defined as one or more processors or cores of the computing elementbeing programmed by a set of software instructions stored in the memoryof the computing element to execute the set of functions on target dataor data objects stored in the memory.

It should be noted that any language directed to a computer should beread to include any suitable combination of computing devices or networkplatforms, including servers, interfaces, systems, databases, agents,peers, engines, controllers, modules, or other types of computingdevices operating individually or collectively. One should appreciatethe computing devices comprise a processor configured to executesoftware instructions stored on a tangible, non-transitory computerreadable storage medium (e.g., hard drive, FPGA, PLA, solid state drive,RAM, flash, ROM, etc.). The software instructions configure or programthe computing device to provide the roles, responsibilities, or otherfunctionality as discussed below with respect to the disclosedapparatus. Further, the disclosed technologies can be embodied as acomputer program product that includes a non-transitory computerreadable medium storing the software instructions that causes aprocessor to execute the disclosed steps associated with implementationsof computer-based algorithms, processes, methods, or other instructions.In some embodiments, the various servers, systems, databases, orinterfaces exchange data using standardized protocols or algorithms,possibly based on HTTP, HTTPS, AES, public-private key exchanges, webservice APIs, known financial transaction protocols, or other electronicinformation exchanging methods. Data exchanges among devices can beconducted over a packet-switched network, the Internet, LAN, WAN, VPN,or other type of packet switched network; a circuit switched network;cell switched network; or other type of network.

A LiDAR device is an important sensor that can provide data used inthree-dimensional perception, autonomous driving, automation, and manyother emerging technologies and industries. The basic operationalprinciple of a LiDAR device is that it transmits laser light toilluminate an object in a field-of-view and receives return light formedfrom the scattered and/or reflected light. The distance to the objectcan be determined based on the time of the transmission light and thetime of the return light. Existing LiDAR devices have many componentsthat may make the device bulky. Thus, it may be difficult to fit anexisting LiDAR device into a compact space such the rear-view mirrorassembly, the light housing, the bumper, or the rooftop. Moreover,existing LiDAR devices often have limited FOVs even when they aremounted into a small space of a vehicle, because the small space limitsthe LiDAR's scanning capabilities. Therefore, there is a need for acompact LiDAR device that can fit into a small space and is stillcapable of performing scanning of a wide FOV.

Embodiments of present disclosure are described below. In variousembodiments, a compact LiDAR device is provided. The compact LiDARdevice comprises a polygon mirror configured to scan an FOV in both thehorizontal and vertical directions, thereby achieving a very compactsize and an ultra-wide FOV. The polygon mirror comprises multiplereflective facets and at least some of the facets have non-90 degreetilt angles. The compact size of the LiDAR device enables the device tobe disposed inside many small spaces in a vehicle including, forexample, the headlight housing, the rear light housing, the rear-viewmirror assemblies, the corners of the vehicle body, etc. In one example,the compact LiDAR device can provide a horizontal FOV of about 120degrees or greater (about 240 degrees for using two such LiDAR devices)and a vertical FOV of about 90 degrees or greater. The compact LiDARdevice can enable scanning multiple detection zones with differentscanning resolutions. A higher scanning resolution is desirable incertain regions-of-interest (ROI) areas. Typical or lower scanningresolution may be used for scanning non-ROI areas. The compact LiDARdevice disclosed herein can dynamically adjust the scanning of ROI areasand non-ROI areas. Various embodiments of the compact LiDAR device aredescribed in more detail below.

FIG. 1 illustrates one or more exemplary LiDAR systems 110 disposed orincluded in a motor vehicle 100. Motor vehicle 100 can be a vehiclehaving any automated level. For example, motor vehicle 100 can be apartially automated vehicle, a highly automated vehicle, a fullyautomated vehicle, or a driverless vehicle. A partially automatedvehicle can perform some driving functions without a human driver'sintervention. For example, a partially automated vehicle can performblind-spot monitoring, lane keeping and/or lane changing operations,automated emergency braking, smart cruising and/or traffic following, orthe like. Certain operations of a partially automated vehicle may belimited to specific applications or driving scenarios (e.g., limited toonly freeway driving). A highly automated vehicle can generally performall operations of a partially automated vehicle but with lesslimitations. A highly automated vehicle can also detect its own limitsin operating the vehicle and ask the driver to take over the control ofthe vehicle when necessary. A fully automated vehicle can perform allvehicle operations without a driver's intervention but can also detectits own limits and ask the driver to take over when necessary. Adriverless vehicle can operate on its own without any driverintervention.

In typical configurations, motor vehicle 100 comprises one or more LiDARsystems 110 and 120A-F. Each of LiDAR systems 110 and 120A-F can be ascanning-based LiDAR system and/or a non-scanning LiDAR system (e.g., aflash LiDAR). A scanning-based LiDAR system scans one or more lightbeams in one or more directions (e.g., horizontal and verticaldirections) to detect objects in a field-of-view (FOV). A non-scanningbased LiDAR system transmits laser light to illuminate an FOV withoutscanning. For example, a flash LiDAR is a type of non-scanning basedLiDAR system. A flash LiDAR can transmit laser light to simultaneouslyilluminate an FOV using a single light pulse or light shot.

A LiDAR system is often an essential sensor of a vehicle that is atleast partially automated. In one embodiment, as shown in FIG. 1, motorvehicle 100 may include a single LiDAR system 110 (e.g., without LiDARsystems 120A-F) disposed at the highest position of the vehicle (e.g.,at the vehicle roof). Disposing LiDAR system 110 at the vehicle rooffacilitates a 360-degree scanning around vehicle 100. In some otherembodiments, motor vehicle 100 can include multiple LiDAR systems,including two or more of systems 110 and/or 120A-F. As shown in FIG. 1,in one embodiment, multiple LiDAR systems 110 and/or 120A-F are attachedto vehicle 100 at different locations of the vehicle. For example, LiDARsystem 120A is attached to vehicle 100 at the front right corner; LiDARsystem 120B is attached to vehicle 100 at the front center; LiDAR system120C is attached to vehicle 100 at the front left corner; LiDAR system120D is attached to vehicle 100 at the right-side rear view mirror;LiDAR system 120E is attached to vehicle 100 at the left-side rear viewmirror; and/or LiDAR system 120F is attached to vehicle 100 at the backcenter. In some embodiments, LiDAR systems 110 and 120A-F areindependent LiDAR systems having their own respective laser sources,control electronics, transmitters, receivers, and/or steeringmechanisms. In other embodiments, some of LiDAR systems 110 and 120A-Fcan share one or more components, thereby forming a distributed sensorsystem. In one example, optical fibers are used to deliver laser lightfrom a centralized laser source to all LiDAR systems. It is understoodthat one or more LiDAR systems can be distributed and attached to avehicle in any desired manner and FIG. 1 only illustrates oneembodiment. As another example, LiDAR systems 120D and 120E may beattached to the B-pillars of vehicle 100 instead of the rear-viewmirrors. As another example, LiDAR system 120B may be attached to thewindshield of vehicle 100 instead of the front bumper.

FIG. 2 is a block diagram 200 illustrating interactions between vehicleonboard LiDAR system(s) 210 and multiple other systems including avehicle perception and planning system 220. LiDAR system(s) 210 can bemounted on or integrated to a vehicle. LiDAR system(s) 210 includesensor(s) that scan laser light to the surrounding environment tomeasure the distance, angle, and/or velocity of objects. Based on thescattered light that returned to LiDAR system(s) 210, it can generatesensor data (e.g., image data or 3D point cloud data) representing theperceived external environment.

LiDAR system(s) 210 can include one or more of short-range LiDARsensors, medium-range LiDAR sensors, and long-range LiDAR sensors. Ashort-range LiDAR sensor measures objects located up to about 20-40meters from the LiDAR sensor. Short-range LiDAR sensors can be used for,e.g., monitoring nearby moving objects (e.g., pedestrians crossingstreet in a school zone), parking assistance applications, or the like.A medium-range LiDAR sensor measures objects located up to about 100-150meters from the LiDAR sensor. Medium-range LiDAR sensors can be usedfor, e.g., monitoring road intersections, assistance for merging onto orleaving a freeway, or the like. A long-range LiDAR sensor measuresobjects located up to about 150-300 meters. Long-range LiDAR sensors aretypically used when a vehicle is travelling at high speed (e.g., on afreeway), such that the vehicle's control systems may only have a fewseconds (e.g., 6-8 seconds) to respond to any situations detected by theLiDAR sensor. As shown in FIG. 2, in one embodiment, the LiDAR sensordata can be provided to vehicle perception and planning system 220 via acommunication path 213 for further processing and controlling thevehicle operations. Communication path 213 can be any wired or wirelesscommunication links that can transfer data.

With reference still to FIG. 2, in some embodiments, other vehicleonboard sensor(s) 230 are used to provide additional sensor dataseparately or together with LiDAR system(s) 210. Other vehicle onboardsensors 230 may include, for example, one or more camera(s) 232, one ormore radar(s) 234, one or more ultrasonic sensor(s) 236, and/or othersensor(s) 238. Camera(s) 232 can take images and/or videos of theexternal environment of a vehicle. Camera(s) 232 can take, for example,high-definition (HD) videos having millions of pixels in each frame. Acamera produces monochrome or color images and videos. Color informationmay be important in interpreting data for some situations (e.g.,interpreting images of traffic lights). Color information may not beavailable from other sensors such as LiDAR or radar sensors. Camera(s)232 can include one or more of narrow-focus cameras, wider-focuscameras, side-facing cameras, infrared cameras, fisheye cameras, or thelike. The image and/or video data generated by camera(s) 232 can also beprovided to vehicle perception and planning system 220 via communicationpath 233 for further processing and controlling the vehicle operations.Communication path 233 can be any wired or wireless communication linksthat can transfer data.

Other vehicle onboard sensos(s) 230 can also include radar sensor(s)234. Radar sensor(s) 234 use radio waves to determine the range, angle,and velocity of objects. Radar sensor(s) 234 produce electromagneticwaves in the radio or microwave spectrum. The electromagnetic wavesreflect off an object and some of the reflected waves return to theradar sensor, thereby providing information about the object's positionand velocity. Radar sensor(s) 234 can include one or more of short-rangeradar(s), medium-range radar(s), and long-range radar(s). A short-rangeradar measures objects located at about 0.1-30 meters from the radar. Ashort-range radar is useful in detecting objects located nearby thevehicle, such as other vehicles, buildings, walls, pedestrians,bicyclists, etc. A short-range radar can be used to detect a blind spot,assist in lane changing, provide rear-end collision warning, assist inparking, provide emergency braking, or the like. A medium-range radarmeasures objects located at about 30-80 meters from the radar. Along-range radar measures objects located at about 80-200 meters.Medium- and/or long-range radars can be useful in, for example, trafficfollowing, adaptive cruise control, and/or highway automatic braking.Sensor data generated by radar sensor(s) 234 can also be provided tovehicle perception and planning system 220 via communication path 233for further processing and controlling the vehicle operations.

Other vehicle onboard sensor(s) 230 can also include ultrasonicsensor(s) 236. Ultrasonic sensor(s) 236 use acoustic waves or pulses tomeasure object located external to a vehicle. The acoustic wavesgenerated by ultrasonic sensor(s) 236 are transmitted to the surroundingenvironment. At least some of the transmitted waves are reflected off anobject and return to the ultrasonic sensor(s) 236. Based on the returnsignals, a distance of the object can be calculated. Ultrasonicsensor(s) 236 can be useful in, for example, check blind spot, identifyparking spots, provide lane changing assistance into traffic, or thelike. Sensor data generated by ultrasonic sensor(s) 236 can also beprovided to vehicle perception and planning system 220 via communicationpath 233 for further processing and controlling the vehicle operations.

In some embodiments, one or more other sensor(s) 238 may be attached ina vehicle and may also generate sensor data. Other sensor(s) 238 mayinclude, for example, global positioning systems (GPS), inertialmeasurement units (IMU), or the like. Sensor data generated by othersensor(s) 238 can also be provided to vehicle perception and planningsystem 220 via communication path 233 for further processing andcontrolling the vehicle operations. It is understood that communicationpath 233 may include one or more communication links to transfer databetween the various sensor(s) 230 and vehicle perception and planningsystem 220.

In some embodiments, as shown in FIG. 2, sensor data from other vehicleonboard sensor(s) 230 can be provided to vehicle onboard LiDAR system(s)210 via communication path 231. LiDAR system(s) 210 may process thesensor data from other vehicle onboard sensor(s) 230. For example,sensor data from camera(s) 232, radar sensor(s) 234, ultrasonicsensor(s) 236, and/or other sensor(s) 238 may be correlated or fusedwith sensor data LiDAR system(s) 210, thereby at least partiallyoffloading the sensor fusion process performed by vehicle perception andplanning system 220. It is understood that other configurations may alsobe implemented for transmitting and processing sensor data from thevarious sensors (e.g., data can be transmitted to a cloud service forprocessing and then the processing results can be transmitted back tothe vehicle perception and planning system 220).

With reference still to FIG. 2, in some embodiments, sensors onboardother vehicle(s) 250 are used to provide additional sensor dataseparately or together with LiDAR system(s) 210. For example, two ormore nearby vehicles may have their own respective LiDAR sensor(s),camera(s), radar sensor(s), ultrasonic sensor(s), etc. Nearby vehiclescan communicate and share sensor data with one another. Communicationsbetween vehicles are also referred to as V2V (vehicle to vehicle)communications. For example, as shown in FIG. 2, sensor data generatedby other vehicle(s) 250 can be communicated to vehicle perception andplanning system 220 and/or vehicle onboard LiDAR system(s) 210, viacommunication path 253 and/or communication path 251, respectively.Communication paths 253 and 251 can be any wired or wirelesscommunication links that can transfer data.

Sharing sensor data facilitates a better perception of the environmentexternal to the vehicles. For instance, a first vehicle may not sense apedestrian that is a behind a second vehicle but is approaching thefirst vehicle. The second vehicle may share the sensor data related tothis pedestrian with the first vehicle such that the first vehicle canhave additional reaction time to avoid collision with the pedestrian. Insome embodiments, similar to data generated by sensor(s) 230, datagenerated by sensors onboard other vehicle(s) 250 may be correlated orfused with sensor data generated by LiDAR system(s) 210, thereby atleast partially offloading the sensor fusion process performed byvehicle perception and planning system 220.

In some embodiments, intelligent infrastructure system(s) 240 are usedto provide sensor data separately or together with LiDAR system(s) 210.Certain infrastructures may be configured to communicate with a vehicleto convey information and vice versa. Communications between a vehicleand infrastructures are generally referred to as V2I (vehicle toinfrastructure) communications. For example, intelligent infrastructuresystem(s) 240 may include an intelligent traffic light that can conveyits status to an approaching vehicle in a message such as “changing toyellow in 5 seconds.” Intelligent infrastructure system(s) 240 may alsoinclude its own LiDAR system mounted near an intersection such that itcan convey traffic monitoring information to a vehicle. For example, aleft-turning vehicle at an intersection may not have sufficient sensingcapabilities because some of its own sensors may be blocked by trafficsin the opposite direction. In such a situation, sensors of intelligentinfrastructure system(s) 240 can provide useful, and sometimes vital,data to the left-turning vehicle. Such data may include, for example,traffic conditions, information of objects in the direction the vehicleis turning to, traffic light status and predictions, or the like. Thesesensor data generated by intelligent infrastructure system(s) 240 can beprovided to vehicle perception and planning system 220 and/or vehicleonboard LiDAR system(s) 210, via communication paths 243 and/or 241,respectively. Communication paths 243 and/or 241 can include any wiredor wireless communication links that can transfer data. For example,sensor data from intelligent infrastructure system(s) 240 may betransmitted to LiDAR system(s) 210 and correlated or fused with sensordata generated by LiDAR system(s) 210, thereby at least partiallyoffloading the sensor fusion process performed by vehicle perception andplanning system 220. V2V and V2I communications described above areexamples of vehicle-to-X (V2X) communications, where the “X” representsany other devices, systems, sensors, infrastructure, or the like thatcan share data with a vehicle.

With reference still to FIG. 2, via various communication paths, vehicleperception and planning system 220 receives sensor data from one or moreof LiDAR system(s) 210, other vehicle onboard sensor(s) 230, othervehicle(s) 250, and/or intelligent infrastructure system(s) 240. In someembodiments, different types of sensor data are correlated and/orintegrated by a sensor fusion sub-system 222. For example, sensor fusionsub-system 222 can generate a 360-degree model using multiple images orvideos captured by multiple cameras disposed at different positions ofthe vehicle. Sensor fusion sub-system 222 obtains sensor data fromdifferent types of sensors and uses the combined data to perceive theenvironment more accurately. For example, a vehicle onboard camera 232may not capture a clear image because it is facing the sun or a lightsource (e.g., another vehicle's headlight during nighttime) directly. ALiDAR system 210 may not be affected as much and therefore sensor fusionsub-system 222 can combine sensor data provided by both camera 232 andLiDAR system 210, and use the sensor data provided by LiDAR system 210to compensate the unclear image captured by camera 232. As anotherexample, in a rainy or foggy weather, a radar sensor 234 may work betterthan a camera 232 or a LiDAR system 210. Accordingly, sensor fusionsub-system 222 may use sensor data provided by the radar sensor 234 tocompensate the sensor data provided by camera 232 or LiDAR system 210.

In other examples, sensor data generated by other vehicle onboardsensor(s) 230 may have a lower resolution (e.g., radar sensor data) andthus may need to be correlated and confirmed by LiDAR system(s) 210,which usually has a higher resolution. For example, a sewage cover (alsoreferred to as a manhole cover) may be detected by radar sensor 234 asan object towards which a vehicle is approaching. Due to thelow-resolution nature of radar sensor 234, vehicle perception andplanning system 220 may not be able to determine whether the object isan obstacle that the vehicle needs to avoid. High-resolution sensor datagenerated by LiDAR system(s) 210 thus can be used to correlated andconfirm that the object is a sewage cover and causes no harm to thevehicle.

Vehicle perception and planning system 220 further comprises an objectclassifier 223. Using raw sensor data and/or correlated/fused dataprovided by sensor fusion sub-system 222, object classifier 223 candetect and classify the objects and estimate the positions of theobjects. In some embodiments, object classifier 233 can usemachine-learning based techniques to detect and classify objects.Examples of the machine-learning based techniques include utilizingalgorithms such as region-based convolutional neural networks (R-CNN),Fast R-CNN, Faster R-CNN, histogram of oriented gradients (HOG),region-based fully convolutional network (R-FCN), single shot detector(SSD), spatial pyramid pooling (SPP-net), and/or You Only Look Once(Yolo).

Vehicle perception and planning system 220 further comprises a roaddetection sub-system 224. Road detection sub-system 224 localizes theroad and identifies objects and/or markings on the road. For example,based on raw or fused sensor data provided by radar sensor(s) 234,camera(s) 232, and/or LiDAR system(s) 210, road detection sub-system 224can build a 3D model of the road based on machine-learning techniques(e.g., pattern recognition algorithms for identifying lanes). Using the3D model of the road, road detection sub-system 224 can identify objects(e.g., obstacles or debris on the road) and/or markings on the road(e.g., lane lines, turning marks, crosswalk marks, or the like).

Vehicle perception and planning system 220 further comprises alocalization and vehicle posture sub-system 225. Based on raw or fusedsensor data, localization and vehicle posture sub-system 225 candetermine position of the vehicle and the vehicle's posture. Forexample, using sensor data from LiDAR system(s) 210, camera(s) 232,and/or GPS data, localization and vehicle posture sub-system 225 candetermine an accurate position of the vehicle on the road and thevehicle's six degrees of freedom (e.g., whether the vehicle is movingforward or backward, up or down, and left or right). In someembodiments, high-definition (HD) maps are used for vehiclelocalization. HD maps can provide highly detailed, three-dimensional,computerized maps that pinpoint a vehicle's location. For instance,using the HD maps, localization and vehicle posture sub-system 225 candetermine precisely the vehicle's current position (e.g., which lane ofthe road the vehicle is currently in, how close it is to a curb or asidewalk) and predict vehicle's future positions.

Vehicle perception and planning system 220 further comprises obstaclepredictor 226. Objects identified by object classifier 223 can bestationary (e.g., a light pole, a road sign) or dynamic (e.g., a movingpedestrian, bicycle, another car). For moving objects, predicting theirmoving path or future positions can be important to avoid collision.Obstacle predictor 226 can predict an obstacle trajectory and/or warnthe driver or the vehicle planning sub-system 228 about a potentialcollision. For example, if there is a high likelihood that theobstacle's trajectory intersects with the vehicle's current moving path,obstacle predictor 226 can generate such a warning. Obstacle predictor226 can use a variety of techniques for making such a prediction. Suchtechniques include, for example, constant velocity or accelerationmodels, constant turn rate and velocity/acceleration models, KalmanFilter and Extended Kalman Filter based models, recurrent neural network(RNN) based models, long short-term memory (LSTM) neural network basedmodels, encoder-decoder RNN models, or the like.

With reference still to FIG. 2, in some embodiments, vehicle perceptionand planning system 220 further comprises vehicle planning sub-system228. Vehicle planning sub-system 228 can include a route planner, adriving behaviors planner, and a motion planner. The route planner canplan the route of a vehicle based on the vehicle's current locationdata, target location data, traffic information, etc. The drivingbehavior planner adjusts the timing and planned movement based on howother objects might move, using the obstacle prediction results providedby obstacle predictor 226. The motion planner determines the specificoperations the vehicle needs to follow. The planning results are thencommunicated to vehicle control system 280 via vehicle interface 270.The communication can be performed through communication paths 223 and271, which include any wired or wireless communication links that cantransfer data.

Vehicle control system 280 controls the vehicle's steering mechanism,throttle, brake, etc., to operate the vehicle according to the plannedroute and movement. Vehicle perception and planning system 220 mayfurther comprise a user interface 260, which provides a user (e.g., adriver) access to vehicle control system 280 to, for example, overrideor take over control of the vehicle when necessary. User interface 260can communicate with vehicle perception and planning system 220, forexample, to obtain and display raw or fused sensor data, identifiedobjects, vehicle's location/posture, etc. These displayed data can helpa user to better operate the vehicle. User interface 260 can communicatewith vehicle perception and planning system 220 and/or vehicle controlsystem 280 via communication paths 221 and 261 respectively, whichinclude any wired or wireless communication links that can transferdata. It is understood that the various systems, sensors, communicationlinks, and interfaces in FIG. 2 can be configured in any desired mannerand not limited to the configuration shown in FIG. 2.

FIG. 3 is a block diagram illustrating an exemplary LiDAR system 300.LiDAR system 300 can be used to implement LiDAR system 110, 120A-F,and/or 210 shown in FIGS. 1 and 2. In one embodiment, LiDAR system 300comprises a laser source 310, a transmitter 320, an optical receiver andlight detector 330, a steering system 340, and a control circuitry 350.These components are coupled together using communications paths 312,314, 322, 332, 343, 352, and 362. These communications paths includecommunication links (wired or wireless, bidirectional or unidirectional)among the various LiDAR system components, but need not be physicalcomponents themselves. While the communications paths can be implementedby one or more electrical wires, buses, or optical fibers, thecommunication paths can also be wireless channels or free-space opticalpaths so that no physical communication medium is present. For example,in one embodiment of LiDAR system 300, communication path 314 betweenlaser source 310 and transmitter 320 may be implemented using one ormore optical fibers. Communication paths 332 and 352 may representoptical paths implemented using free space optical components and/oroptical fibers. And communication paths 312, 322, 342, and 362 may beimplemented using one or more electrical wires that carry electricalsignals. The communications paths can also include one or more of theabove types of communication mediums (e.g., they can include an opticalfiber and a free-space optical component, or include one or more opticalfibers and one or more electrical wires).

LiDAR system 300 can also include other components not depicted in FIG.3, such as power buses, power supplies, LED indicators, switches, etc.Additionally, other communication connections among components may bepresent, such as a direct connection between light source 310 andoptical receiver and light detector 330 to provide a reference signal sothat the time from when a light pulse is transmitted until a returnlight pulse is detected can be accurately measured.

Laser source 310 outputs laser light for illuminating objects in a fieldof view (FOV). Laser source 310 can be, for example, asemiconductor-based laser (e.g., a diode laser) and/or a fiber-basedlaser. A semiconductor-based laser can be, for example, an edge emittinglaser (EEL), a vertical cavity surface emitting laser (VCSEL), or thelike. A fiber-based laser is a laser in which the active gain medium isan optical fiber doped with rare-earth elements such as erbium,ytterbium, neodymium, dysprosium, praseodymium, thulium and/or holmium.In some embodiments, a fiber laser is based on double-clad fibers, inwhich the gain medium forms the core of the fiber surrounded by twolayers of cladding. The double-clad fiber allows the core to be pumpedwith a high-power beam, thereby enabling the laser source to be a highpower fiber laser source.

In some embodiments, laser source 310 comprises a master oscillator(also referred to as a seed laser) and power amplifier (MOPA). The poweramplifier amplifies the output power of the seed laser. The poweramplifier can be a fiber amplifier, a bulk amplifier, or a semiconductoroptical amplifier. The seed laser can be a diode laser (e.g., aFabry-Perot cavity laser, a distributed feedback laser), a solid-statebulk laser, or a tunable external-cavity diode laser. In someembodiments, laser source 310 can be an optically pumped microchiplaser. Microchip lasers are alignment-free monolithic solid-state laserswhere the laser crystal is directly contacted with the end mirrors ofthe laser resonator. A microchip laser is typically pumped with a laserdiode (directly or using a fiber) to obtain the desired output power. Amicrochip laser can be based on neodymium-doped yttrium aluminum garnet(Y₃Al₅O₁₂) laser crystals (i.e., Nd:YAG), or neodymium-doped vanadate(i.e., ND:YVO₄) laser crystals.

FIG. 4 is a block diagram illustrating an exemplary fiber-based lasersource 400 having a seed laser and one or more pumps (e.g., laserdiodes) for pumping desired output power. Fiber-based laser source 400is an example of laser source 310 depicted in FIG. 3. In someembodiments, fiber-based laser source 400 comprises a seed laser 402 togenerate initial light pulses of one or more wavelengths (e.g., 1550nm), which are provided to a wavelength-division multiplexor (WDM) 404via an optical fiber 403. Fiber-based laser source 400 further comprisesa pump 406 for providing laser power (e.g., of a different wavelength,such as 980 nm) to WDM 404 via an optical fiber 405. WDM 404 multiplexesthe light pulses provided by seed laser 402 and the laser power providedby pump 406 onto a single optical fiber 407. The output of WDM 404 canthen be provided to one or more pre-amplifier(s) 408 via optical fiber407. Pre-amplifier(s) 408 can be optical amplifier(s) that amplifyoptical signals (e.g., with about 20-30 dB gain). In some embodiments,pre-amplifier(s) 408 are low noise amplifiers. Pre-amplifier(s) 408output to a combiner 410 via an optical fiber 409. Combiner 410 combinesthe output laser light of pre-amplifier(s) 408 with the laser powerprovided by pump 412 via an optical fiber 411. Combiner 410 can combineoptical signals having the same wavelength or different wavelengths. Oneexample of a combiner is a WDM. Combiner 410 provides pulses to abooster amplifier 414, which produces output light pulses via opticalfiber 410. The booster amplifier 414 provides further amplification ofthe optical signals. The outputted light pulses can then be transmittedto transmitter 320 and/or steering mechanism 340 (shown in FIG. 3). Itis understood that FIG. 4 illustrates one exemplary configuration offiber-based laser source 400. Laser source 400 can have many otherconfigurations using different combinations of one or more componentsshown in FIG. 4 and/or other components not shown in FIG. 4 (e.g., othercomponents such as power supplies, lens, filters, splitters, combiners,etc.).

In some variations, fiber-based laser source 400 can be controlled(e.g., by control circuitry 350) to produce pulses of differentamplitudes based on the fiber gain profile of the fiber used infiber-based laser source 400. Communication path 312 couples fiber-basedlaser source 400 to control circuitry 350 (shown in FIG. 3) so thatcomponents of fiber-based laser source 400 can be controlled by orotherwise communicate with control circuitry 350. Alternatively,fiber-based laser source 400 may include its own dedicated controller.Instead of control circuitry 350 communicating directly with componentsof fiber-based laser source 400, a dedicated controller of fiber-basedlaser source 400 communicates with control circuitry 350 and controlsand/or communicates with the components of fiber-based light source 400.Fiber-based light source 400 can also include other components notshown, such as one or more power connectors, power supplies, and/orpower lines.

Referencing FIG. 3, typical operating wavelengths of laser source 310comprise, for example, about 850 nm, about 905 nm, about 940 nm, about1064 nm, and about 1550 nm. The upper limit of maximum usable laserpower is set by the U.S. FDA (U.S. Food and Drug Administration)regulations. The optical power limit at 1550 nm wavelength is muchhigher than those of the other aforementioned wavelengths. Further, at1550 nm, the optical power loss in a fiber is low. There characteristicsof the 1550 nm wavelength make it more beneficial for long-range LiDARapplications. The amount of optical power output from laser source 310can be characterized by its peak power, average power, and the pulseenergy. The peak power is the ratio of pulse energy to the width of thepulse (e.g., full width at half maximum or FWHM). Thus, a smaller pulsewidth can provide a larger peak power for a fixed amount of pulseenergy. A pulse width can be in the range of nanosecond or picosecond.The average power is the product of the energy of the pulse and thepulse repetition rate (PRR). As described in more detail below, the PRRrepresents the frequency of the pulsed laser light. The PRR typicallycorresponds to the maximum range that a LiDAR system can measure. Lasersource 310 can be configured to produce pulses at high PRR to meet thedesired number of data points in a point cloud generated by the LiDARsystem. Laser source 310 can also be configured to produce pulses atmedium or low PRR to meet the desired maximum detection distance. Wallplug efficiency (WPE) is another factor to evaluate the total powerconsumption, which may be a key indicator in evaluating the laserefficiency. For example, as shown in FIG. 1, multiple LiDAR systems maybe attached to a vehicle, which may be an electrical-powered vehicle ora vehicle otherwise having limited fuel or battery power supply.Therefore, high WPE and intelligent ways to use laser power are oftenamong the important considerations when selecting and configuring lasersource 310 and/or designing laser delivery systems for vehicle-mountedLiDAR applications.

It is understood that the above descriptions provide non-limitingexamples of a laser source 310. Laser source 310 can be configured toinclude many other types of light sources (e.g., laser diodes,short-cavity fiber lasers, solid-state lasers, and/or tunable externalcavity diode lasers) that are configured to generate one or more lightsignals at various wavelengths. In some examples, light source 310comprises amplifiers (e.g., pre-amplifiers and/or booster amplifiers),which can be a doped optical fiber amplifier, a solid-state bulkamplifier, and/or a semiconductor optical amplifier. The amplifiers areconfigured to receive and amplify light signals with desired gains.

With reference back to FIG. 3, LiDAR system 300 further comprises atransmitter 320. Laser source 310 provides laser light (e.g., in theform of a laser beam) to transmitter 320. The laser light provided bylaser source 310 can be amplified laser light with a predetermined orcontrolled wavelength, pulse repetition rate, and/or power level.Transmitter 320 receives the laser light from laser source 310 andtransmits the laser light to steering mechanism 340 with low divergence.In some embodiments, transmitter 320 can include, for example, opticalcomponents (e.g., lens, fibers, mirrors, etc.) for transmitting laserbeams to a field-of-view (FOV) directly or via steering mechanism 340.While FIG. 3 illustrates transmitter 320 and steering mechanism 340 asseparate components, they may be combined or integrated as one system insome embodiments. Steering mechanism 340 is described in more detailbelow.

Laser beams provided by laser source 310 may diverge as they travel totransmitter 320. Therefore, transmitter 320 often comprises acollimating lens configured to collect the diverging laser beams andproduce more parallel optical beams with reduced or minimum divergence.The collimated optical beams can then be further directed throughvarious optics such as mirrors and lens. A collimating lens may be, forexample, a single plano-convex lens or a lens group. The collimatinglens can be configured to achieve any desired properties such as thebeam diameter, divergence, numerical aperture, focal length, or thelike. A beam propagation ratio or beam quality factor (also referred toas the M² factor) is used for measurement of laser beam quality. In manyLiDAR applications, it is important to have good laser beam quality inthe generated transmitting laser beam. The M² factor represents a degreeof variation of a beam from an ideal Gaussian beam. Thus, the M² factorreflects how well a collimated laser beam can be focused on a smallspot, or how well a divergent laser beam can be collimated. Therefore,laser source 310 and/or transmitter 320 can be configured to meet, forexample, a scan resolution requirement while maintaining the desired M²factor.

One or more of the light beams provided by transmitter 320 are scannedby steering mechanism 340 to a FOV. Steering mechanism 340 scans lightbeams in multiple dimensions (e.g., in both the horizontal and verticaldimension) to facilitate LiDAR system 300 to map the environment bygenerating a 3D point cloud. Steering mechanism 340 will be described inmore detail below. The laser light scanned to an FOV may be scattered orreflected by an object in the FOV. At least a portion of the scatteredor reflected light returns to LiDAR system 300. FIG. 3 furtherillustrates an optical receiver and light detector 330 configured toreceive the return light. Optical receiver and light detector 330comprises an optical receiver that is configured to collect the returnlight from the FOV. The optical receiver can include optics (e.g., lens,fibers, mirrors, etc.) for receiving, redirecting, focus, amplifying,and/or filtering return light from the FOV. For example, the opticalreceiver often includes a collection lens (e.g., a single plano-convexlens or a lens group) to collect and/or focus the collected return lightonto a light detector.

A light detector detects the return light focused by the opticalreceiver and generates current and/or voltage signals proportional tothe incident intensity of the return light. Based on such current and/orvoltage signals, the depth information of the object in the FOV can bederived. One exemplary method for deriving such depth information isbased on the direct TOF (time of flight), which is described in moredetail below. A light detector may be characterized by its detectionsensitivity, quantum efficiency, detector bandwidth, linearity, signalto noise ratio (SNR), overload resistance, interference immunity, etc.Based on the applications, the light detector can be configured orcustomized to have any desired characteristics. For example, opticalreceiver and light detector 330 can be configured such that the lightdetector has a large dynamic range while having a good linearity. Thelight detector linearity indicates the detector's capability ofmaintaining linear relationship between input optical signal power andthe detector's output. A detector having good linearity can maintain alinear relationship over a large dynamic input optical signal range.

To achieve desired detector characteristics, configurations orcustomizations can be made to the light detector's structure and/or thedetector's material system. Various detector structure can be used for alight detector. For example, a light detector structure can be a PINbased structure, which has a undoped intrinsic semiconductor region(i.e., an “i” region) between a p-type semiconductor and an n-typesemiconductor region. Other light detector structures comprise, forexample, a APD (avalanche photodiode) based structure, a PMT(photomultiplier tube) based structure, a SiPM (Silicon photomultiplier)based structure, a SPAD (single-photon avalanche diode) base structure,and/or quantum wires. For material systems used in a light detector, Si,InGaAs, and/or Si/Ge based materials can be used. It is understood thatmany other detector structures and/or material systems can be used inoptical receiver and light detector 330.

A light detector (e.g., an APD based detector) may have an internal gainsuch that the input signal is amplified when generating an outputsignal. However, noise may also be amplified due to the light detector'sinternal gain. Common types of noise include signal shot noise, darkcurrent shot noise, thermal noise, and amplifier noise (TIA). In someembodiments, optical receiver and light detector 330 may include apre-amplifier that is a low noise amplifier (LNA). In some embodiments,the pre-amplifier may also include a TIA-transimpedance amplifier, whichconverts a current signal to a voltage signal. For a linear detectorsystem, input equivalent noise or noise equivalent power (NEP) measureshow sensitive the light detector is to weak signals. Therefore, they canbe used as indicators of the overall system performance. For example,the NEP of a light detector specifies the power of the weakest signalthat can be detected and therefore it in turn specifies the maximumrange of a LiDAR system. It is understood that various light detectoroptimization techniques can be used to meet the requirement of LiDARsystem 300. Such optimization techniques may include selecting differentdetector structures, materials, and/or implement signal processingtechniques (e.g., filtering, noise reduction, amplification, or thelike). For example, in addition to or instead of using direct detectionof return signals (e.g., by using TOF), coherent detection can also beused for a light detector. Coherent detection allows for detectingamplitude and phase information of the received light by interfering thereceived light with a local oscillator. Coherent detection can improvedetection sensitivity and noise immunity.

FIG. 3 further illustrates that LiDAR system 300 comprises steeringmechanism 340. As described above, steering mechanism 340 directs lightbeams from transmitter 320 to scan an FOV in multiple dimensions. Asteering mechanism is referred to as a raster mechanism or a scanningmechanism. Scanning light beams in multiple directions (e.g., in boththe horizontal and vertical directions) facilitates a LiDAR system tomap the environment by generating an image or a 3D point cloud. Asteering mechanism can be based on mechanical scanning and/orsolid-state scanning. Mechanical scanning uses rotating mirrors to steerthe laser beam or physically rotate the LiDAR transmitter and receiver(collectively referred to as transceiver) to scan the laser beam.Solid-state scanning directs the laser beam to various positions throughthe FOV without mechanically moving any macroscopic components such asthe transceiver. Solid-state scanning mechanisms include, for example,optical phased arrays based steering and flash LiDAR based steering. Insome embodiments, because solid-state scanning mechanisms do notphysically move macroscopic components, the steering performed by asolid-state scanning mechanism may be referred to as effective steering.A LiDAR system using solid-state scanning may also be referred to as anon-mechanical scanning or simply non-scanning LiDAR system (a flashLiDAR system is an exemplary non-scanning LiDAR system).

Steering mechanism 340 can be used with the transceiver (e.g.,transmitter 320 and optical receiver and light detector 330) to scan theFOV for generating an image or a 3D point cloud. As an example, toimplement steering mechanism 340, a two-dimensional mechanical scannercan be used with a single-point or several single-point transceivers. Asingle-point transceiver transmits a single light beam or a small numberof light beams (e.g., 2-8 beams) to the steering mechanism. Atwo-dimensional mechanical steering mechanism comprises, for example,polygon mirror(s), oscillating mirror(s), rotating prism(s), rotatingtilt mirror surface(s), or a combination thereof. In some embodiments,steering mechanism 340 may include non-mechanical steering mechanism(s)such as solid-state steering mechanism(s). For example, steeringmechanism 340 can be based on tuning wavelength of the laser lightcombined with refraction effect, and/or based on reconfigurablegrating/phase array. In some embodiments, steering mechanism 340 can usea single scanning device to achieve two-dimensional scanning or twodevices combined to realize two-dimensional scanning.

As another example, to implement steering mechanism 340, aone-dimensional mechanical scanner can be used with an array or a largenumber of single-point transceivers. Specifically, the transceiver arraycan be mounted on a rotating platform to achieve 360-degree horizontalfield of view. Alternatively, a static transceiver array can be combinedwith the one-dimensional mechanical scanner. A one-dimensionalmechanical scanner comprises polygon mirror(s), oscillating mirror(s),rotating prism(s), rotating tilt mirror surface(s) for obtaining aforward-looking horizontal field of view. Steering mechanisms usingmechanical scanners can provide robustness and reliability in highvolume production for automotive applications.

As another example, to implement steering mechanism 340, atwo-dimensional transceiver can be used to generate a scan image or a 3Dpoint cloud directly. In some embodiments, a stitching or micro shiftmethod can be used to improve the resolution of the scan image or thefield of view being scanned. For example, using a two-dimensionaltransceiver, signals generated at one direction (e.g., the horizontaldirection) and signals generated at the other direction (e.g., thevertical direction) may be integrated, interleaved, and/or matched togenerate a higher or full resolution image or 3D point cloudrepresenting the scanned FOV.

Some implementations of steering mechanism 340 comprise one or moreoptical redirection elements (e.g., mirrors or lens) that steer returnlight signals (e.g., by rotating, vibrating, or directing) along areceive path to direct the return light signals to optical receiver andlight detector 330. The optical redirection elements that direct lightsignals along the transmitting and receiving paths may be the samecomponents (e.g., shared), separate components (e.g., dedicated), and/ora combination of shared and separate components. This means that in somecases the transmitting and receiving paths are different although theymay partially overlap (or in some cases, substantially overlap).

With reference still to FIG. 3, LiDAR system 300 further comprisescontrol circuitry 350. Control circuitry 350 can be configured and/orprogrammed to control various parts of the LiDAR system 300 and/or toperform signal processing. In a typical system, control circuitry 350can be configured and/or programmed to perform one or more controloperations including, for example, controlling laser source 310 toobtain desired laser pulse timing, repetition rate, and power;controlling steering mechanism 340 (e.g., controlling the speed,direction, and/or other parameters) to scan the FOV and maintain pixelregistration/alignment; controlling optical receiver and light detector330 (e.g., controlling the sensitivity, noise reduction, filtering,and/or other parameters) such that it is an optimal state; andmonitoring overall system health/status for functional safety.

Control circuitry 350 can also be configured and/or programmed toperform signal processing to the raw data generated by optical receiverand light detector 330 to derive distance and reflectance information,and perform data packaging and communication to vehicle perception andplanning system 220 (shown in FIG. 2). For example, control circuitry350 determines the time it takes from transmitting a light pulse until acorresponding return light pulse is received; determines when a returnlight pulse is not received for a transmitted light pulse; determinesthe direction (e.g., horizontal and/or vertical information) for atransmitted/return light pulse; determines the estimated range in aparticular direction; and/or determines any other type of data relevantto LiDAR system 300.

LiDAR system 300 can be disposed in a vehicle, which may operate in manydifferent environments including hot or cold weather, rough roadconditions that may cause intense vibration, high or low humidifies,dusty areas, etc. Therefore, in some embodiments, optical and/orelectronic components of LiDAR system 300 (e.g., optics in transmitter320, optical receiver and light detector 330, and steering mechanism340) are disposed or configured in such a manner to maintain long termmechanical and optical stability. For example, components in LiDARsystem 300 may be secured and sealed such that they can operate underall conditions a vehicle may encounter. As an example, an anti-moisturecoating and/or hermetic sealing may be applied to optical components oftransmitter 320, optical receiver and light detector 330, and steeringmechanism 340 (and other components that are susceptible to moisture).As another example, housing(s), enclosure(s), and/or window can be usedin LiDAR system 300 for providing desired characteristics such ashardness, ingress protection (IP) rating, self-cleaning capability,resistance to chemical and resistance to impact, or the like. Inaddition, efficient and economical methodologies for assembling LiDARsystem 300 may be used to meet the LiDAR operating requirements whilekeeping the cost low.

It is understood by a person of ordinary skill in the art that FIG. 3and the above descriptions are for illustrative purposes only, and aLiDAR system can include other functional units, blocks, or segments,and can include variations or combinations of these above functionalunits, blocks, or segments. For example, LiDAR system 300 can alsoinclude other components not depicted in FIG. 3, such as power buses,power supplies, LED indicators, switches, etc. Additionally, otherconnections among components may be present, such as a direct connectionbetween light source 310 and optical receiver and light detector 330 sothat light detector 330 can accurately measure the time from when lightsource 310 transmits a light pulse until light detector 330 detects areturn light pulse.

These components shown in FIG. 3 are coupled together usingcommunications paths 312, 314, 322, 332, 342, 352, and 362. Thesecommunications paths represent communication (bidirectional orunidirectional) among the various LiDAR system components but need notbe physical components themselves. While the communications paths can beimplemented by one or more electrical wires, busses, or optical fibers,the communication paths can also be wireless channels or open-airoptical paths so that no physical communication medium is present. Forexample, in one exemplary LiDAR system, communication path 314 includesone or more optical fibers; communication path 352 represents an opticalpath; and communication paths 312, 322, 342, and 362 are all electricalwires that carry electrical signals. The communication paths can alsoinclude more than one of the above types of communication mediums (e.g.,they can include an optical fiber and an optical path, or one or moreoptical fibers and one or more electrical wires).

As described above, some LiDAR systems use the time-of-flight (TOF) oflight signals (e.g., light pulses) to determine the distance to objectsin a light path. For example, with reference to FIG. 5A, an exemplaryLiDAR system 500 includes a laser light source (e.g., a fiber laser), asteering system (e.g., a system of one or more moving mirrors), and alight detector (e.g., a photon detector with one or more optics). LiDARsystem 500 can be implemented using, for example, LiDAR system 300described above. LiDAR system 500 transmits a light pulse 502 alonglight path 504 as determined by the steering system of LiDAR system 500.In the depicted example, light pulse 502, which is generated by thelaser light source, is a short pulse of laser light. Further, the signalsteering system of the LiDAR system 500 is a pulsed-signal steeringsystem. However, it should be appreciated that LiDAR systems can operateby generating, transmitting, and detecting light signals that are notpulsed and derive ranges to an object in the surrounding environmentusing techniques other than time-of-flight. For example, some LiDARsystems use frequency modulated continuous waves (i.e., “FMCW”). Itshould be further appreciated that any of the techniques describedherein with respect to time-of-flight based systems that use pulsedsignals also may be applicable to LiDAR systems that do not use one orboth of these techniques.

Referring back to FIG. 5A (e.g., illustrating a time-of-flight LiDARsystem that uses light pulses), when light pulse 502 reaches object 506,light pulse 502 scatters or reflects to generate a return light pulse508. Return light pulse 508 may return to system 500 along light path510. The time from when transmitted light pulse 502 leaves LiDAR system500 to when return light pulse 508 arrives back at LiDAR system 500 canbe measured (e.g., by a processor or other electronics, such as controlcircuitry 350, within the LiDAR system). This time-of-flight combinedwith the knowledge of the speed of light can be used to determine therange/distance from LiDAR system 500 to the portion of object 506 wherelight pulse 502 scattered or reflected.

By directing many light pulses, as depicted in FIG. 5B, LiDAR system 500scans the external environment (e.g., by directing light pulses 502,522, 526, 530 along light paths 504, 524, 528, 532, respectively). Asdepicted in FIG. 5C, LiDAR system 500 receives return light pulses 508,542, 548 (which correspond to transmitted light pulses 502, 522, 530,respectively). Return light pulses 508, 542, and 548 are generated byscattering or reflecting the transmitted light pulses by one of objects506 and 514. Return light pulses 508, 542, and 548 may return to LiDARsystem 500 along light paths 510, 544, and 546, respectively. Based onthe direction of the transmitted light pulses (as determined by LiDARsystem 500) as well as the calculated range from LiDAR system 500 to theportion of objects that scatter or reflect the light pulses (e.g., theportions of objects 506 and 514), the external environment within thedetectable range (e.g., the field of view between path 504 and 532,inclusively) can be precisely mapped or plotted (e.g., by generating a3D point cloud or images).

If a corresponding light pulse is not received for a particulartransmitted light pulse, then it may be determined that there are noobjects within a detectable range of LiDAR system 500 (e.g., an objectis beyond the maximum scanning distance of LiDAR system 500). Forexample, in FIG. 5B, light pulse 526 may not have a corresponding returnlight pulse (as illustrated in FIG. 5C) because light pulse 526 may notproduce a scattering event along its transmission path 528 within thepredetermined detection range. LiDAR system 500, or an external systemin communication with LiDAR system 500 (e.g., a cloud system orservice), can interpret the lack of return light pulse as no objectbeing disposed along light path 528 within the detectable range of LiDARsystem 500.

In FIG. 5B, light pulses 502, 522, 526, and 530 can be transmitted inany order, serially, in parallel, or based on other timings with respectto each other. Additionally, while FIG. 5B depicts transmitted lightpulses as being directed in one dimension or one plane (e.g., the planeof the paper), LiDAR system 500 can also direct transmitted light pulsesalong other dimension(s) or plane(s). For example, LiDAR system 500 canalso direct transmitted light pulses in a dimension or plane that isperpendicular to the dimension or plane shown in FIG. 5B, therebyforming a 2-dimensional transmission of the light pulses. This2-dimensional transmission of the light pulses can be point-by-point,line-by-line, all at once, or in some other manner. A point cloud orimage from a 1-dimensional transmission of light pulses (e.g., a singlehorizontal line) can generate 2-dimensional data (e.g., (1) data fromthe horizontal transmission direction and (2) the range or distance toobjects). Similarly, a point cloud or image from a 2-dimensionaltransmission of light pulses can generate 3-dimensional data (e.g., (1)data from the horizontal transmission direction, (2) data from thevertical transmission direction, and (3) the range or distance toobjects). In general, a LiDAR system performing an n-dimensionaltransmission of light pulses generates (n+1) dimensional data. This isbecause the LiDAR system can measure the depth of an object or therange/distance to the object, which provides the extra dimension ofdata. Therefore, a 2D scanning by a LiDAR system can generate a 3D pointcloud for mapping the external environment of the LiDAR system.

The density of a point cloud refers to the number of measurements (datapoints) per area performed by the LiDAR system. A point cloud densityrelates to the LiDAR scanning resolution. Typically, a larger pointcloud density, and therefore a higher resolution, is desired at leastfor the region of interest (ROI). The density of points in a point cloudor image generated by a LiDAR system is equal to the number of pulsesdivided by the field of view. In some embodiments, the field of view canbe fixed. Therefore, to increase the density of points generated by oneset of transmission-receiving optics (or transceiver optics), the LiDARsystem may need to generate a pulse more frequently. In other words, alight source with a higher pulse repetition rate (PRR) is needed. On theother hand, by generating and transmitting pulses more frequently, thefarthest distance that the LiDAR system can detect may be limited. Forexample, if a return signal from a distant object is received after thesystem transmits the next pulse, the return signals may be detected in adifferent order than the order in which the corresponding signals aretransmitted, thereby causing ambiguity if the system cannot correctlycorrelate the return signals with the transmitted signals.

To illustrate, consider an exemplary LiDAR system that can transmitlaser pulses with a repetition rate between 500 kHz and 1 MHz. Based onthe time it takes for a pulse to return to the LiDAR system and to avoidmix-up of return pulses from consecutive pulses in a conventional LiDARdesign, the farthest distance the LiDAR system can detect may be 300meters and 150 meters for 500 kHz and 1 MHz, respectively. The densityof points of a LiDAR system with 500 kHz repetition rate is half of thatwith 1 MHz. Thus, this example demonstrates that, if the system cannotcorrectly correlate return signals that arrive out of order, increasingthe repetition rate from 500 kHz to 1 MHz (and thus improving thedensity of points of the system) may reduce the detection range of thesystem. Various techniques are used to mitigate the tradeoff betweenhigher PRR and limited detection range. For example, multiplewavelengths can be used for detecting objects in different ranges.Optical and/or signal processing techniques are also used to correlatebetween transmitted and return light signals.

Various systems, apparatus, and methods described herein may beimplemented using digital circuitry, or using one or more computersusing well-known computer processors, memory units, storage devices,computer software, and other components. Typically, a computer includesa processor for executing instructions and one or more memories forstoring instructions and data. A computer may also include, or becoupled to, one or more mass storage devices, such as one or moremagnetic disks, internal hard disks and removable disks, magneto-opticaldisks, optical disks, etc.

Various systems, apparatus, and methods described herein may beimplemented using computers operating in a client-server relationship.Typically, in such a system, the client computers are located remotelyfrom the server computers and interact via a network. The client-serverrelationship may be defined and controlled by computer programs runningon the respective client and server computers. Examples of clientcomputers can include desktop computers, workstations, portablecomputers, cellular smartphones, tablets, or other types of computingdevices.

Various systems, apparatus, and methods described herein may beimplemented using a computer program product tangibly embodied in aninformation carrier, e.g., in a non-transitory machine-readable storagedevice, for execution by a programmable processor; and the methodprocesses and steps described herein, including one or more of the stepsof FIG. 12, may be implemented using one or more computer programs thatare executable by such a processor. A computer program is a set ofcomputer program instructions that can be used, directly or indirectly,in a computer to perform a certain activity or bring about a certainresult. A computer program can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment.

A high-level block diagram of an exemplary apparatus that may be used toimplement systems, apparatus and methods described herein is illustratedin FIG. 6. Apparatus 600 comprises a processor 610 operatively coupledto a persistent storage device 620 and a main memory device 630.Processor 610 controls the overall operation of apparatus 600 byexecuting computer program instructions that define such operations. Thecomputer program instructions may be stored in persistent storage device620, or other computer-readable medium, and loaded into main memorydevice 630 when execution of the computer program instructions isdesired. For example, processor 610 may be used to implement one or morecomponents and systems described herein, such as control circuitry 350(shown in FIG. 3), vehicle perception and planning system 220 (shown inFIG. 2), and vehicle control system 280 (shown in FIG. 2). Thus, themethod steps of FIG. 12 can be defined by the computer programinstructions stored in main memory device 630 and/or persistent storagedevice 620 and controlled by processor 610 executing the computerprogram instructions. For example, the computer program instructions canbe implemented as computer executable code programmed by one skilled inthe art to perform an algorithm defined by the method steps of FIG. 12.Accordingly, by executing the computer program instructions, theprocessor 610 executes an algorithm defined by the methods of FIGS. 3-5and 12. Apparatus 600 also includes one or more network interfaces 680for communicating with other devices via a network. Apparatus 600 mayalso include one or more input/output devices 690 that enable userinteraction with apparatus 600 (e.g., display, keyboard, mouse,speakers, buttons, etc.).

Processor 610 may include both general and special purposemicroprocessors and may be the sole processor or one of multipleprocessors of apparatus 600. Processor 610 may comprise one or morecentral processing units (CPUs), and one or more graphics processingunits (GPUs), which, for example, may work separately from and/ormulti-task with one or more CPUs to accelerate processing, e.g., forvarious image processing applications described herein. Processor 610,persistent storage device 620, and/or main memory device 630 mayinclude, be supplemented by, or incorporated in, one or moreapplication-specific integrated circuits (ASICs) and/or one or morefield programmable gate arrays (FPGAs).

Persistent storage device 620 and main memory device 630 each comprise atangible non-transitory computer readable storage medium. Persistentstorage device 620, and main memory device 630, may each includehigh-speed random access memory, such as dynamic random access memory(DRAM), static random access memory (SRAM), double data rate synchronousdynamic random access memory (DDR RAM), or other random access solidstate memory devices, and may include non-volatile memory, such as oneor more magnetic disk storage devices such as internal hard disks andremovable disks, magneto-optical disk storage devices, optical diskstorage devices, flash memory devices, semiconductor memory devices,such as erasable programmable read-only memory (EPROM), electricallyerasable programmable read-only memory (EEPROM), compact disc read-onlymemory (CD-ROM), digital versatile disc read-only memory (DVD-ROM)disks, or other non-volatile solid state storage devices.

Input/output devices 690 may include peripherals, such as a printer,scanner, display screen, etc. For example, input/output devices 690 mayinclude a display device such as a cathode ray tube (CRT), plasma orliquid crystal display (LCD) monitor for displaying information to auser, a keyboard, and a pointing device such as a mouse or a trackballby which the user can provide input to apparatus 600.

Any or all of the functions of the systems and apparatuses discussedherein may be performed by processor 610, and/or incorporated in, anapparatus or a system such as LiDAR system 300. Further, LiDAR system300 and/or apparatus 600 may utilize one or more neural networks orother deep-learning techniques performed by processor 610 or othersystems or apparatuses discussed herein.

One skilled in the art will recognize that an implementation of anactual computer or computer system may have other structures and maycontain other components as well, and that FIG. 6 is a high-levelrepresentation of some of the components of such a computer forillustrative purposes.

FIG. 7A illustrates a simplified compact LiDAR device 700. Device 700comprises a transceiver array 702, a mirror 704, and a polygon mirror710. The transceiver array 702 comprises one or more transmitterproviding one or more transmission light beams 713. Transceiver array702 also includes one or more receivers for receiving return light. Inthe embodiment shown in FIG. 7A, the transmitters in the transceiverarray 702 transmit multiple laser light beams 713, which are directedtoward mirror 704. For example, the transceiver array 702 may transmit2, 4, 6, 8, 16 light beams, thereby increasing the scanning resolutionand speed. In one example, mirror 704 can be an un-moveable mirror(e.g., a mirror with a fixed position and orientation). In anotherexample, mirror 704 can be a galvanometer mirror controllable tooscillate about an axis of mirror 704. If mirror 704 is an un-moveablemirror, the LiDAR device may overall have a smaller size than if mirror704 is a galvanometer mirror. This is because a galvanometer mirrorrequires a motor to oscillate the mirror. Therefore, to make the LiDARdevice more compact, an un-moveable mirror 704 can be used. If morespace is available and a galvanometer mirror can be used as mirror 704,the oscillation of mirror 704 can facilitate increasing resolution ofthe LiDAR scan lines and increasing the vertical and/or horizontal FOVs.

As shown in FIG. 7A, mirror 704 reflects transmission light beams 713 toform transmission light 715. Transmission light 715 can include one ormore transmission light beams. Light 715 is directed toward polygonmirror 710 for steering light to illuminate objects in an FOV 720.Polygon mirror 710 is thus optically coupled to mirror 704 and rotatesabout an axis 712 to steer light. In some embodiments, polygon mirror710 comprises a plurality of reflective facets, for example, four, five,six, etc. facets. FIGS. 7A and 7B illustrate that polygon mirror 710 hasfour facets (e.g., two such facets 716A and 716B are shown in FIG. 7B).In some embodiments, multiple transmission light beams of light 715 aredirected toward the same facet of polygon mirror 710 at any particulartime. The same facet of polygon mirror 710 then redirects the lightbeams to form light 717. In some embodiments, multiple transmissionlight beams of light 715 are directed toward two or more facets ofpolygon mirror 710 at a particular time. Polygon mirror 710 thenredirect the beams of light 715 to form transmission light 717.

As shown in FIG. 7A, light 717 comprises one or more transmission lightbeams. The combination of the mirror 704 and polygon mirror 710 cansteer light 717 both horizontally and vertically to illuminate objectslocated in an FOV 720. In some embodiments, if mirror 704 is moveable,the movement of mirror 704 enables scanning light 717 in one direction(e.g., the vertical direction) and the movement of polygon mirror 710enables scanning light 717 in another direction (e.g., the horizontaldirection). In other embodiments, mirror 704 is un-moveable andtherefore polygon mirror 710 is configured to enable the scanning inboth horizontal and vertical directions. For example, facets of polygonmirror 710 can be configured to have different tilt angles such thatwhen polygon mirror rotates about axis 712, it can direct light 717 inboth horizontal and vertical directions. The configuration examples ofpolygon mirror 710 are described in greater detail below.

FIG. 7B illustrates a zoom-in view of the polygon mirror 710 used in thecompact LiDAR device 700 shown in FIG. 7A, according to someembodiments. In some embodiments, polygon mirror 710 comprises a topsurface 718, a bottom surface 714, and multiple reflective facets 716A-D(collectively as 716) that reflect light. Reflective facets 716 aredisposed between the top and bottom surfaces of polygon mirror 710 andare therefore also referred to as side surfaces of polygon mirror 710.One embodiment of the polygon mirror 710 is shown in FIG. 7B, where ithas a polygon-shaped top and bottom surfaces (e.g., square-shaped,rectangle-shaped, pentagon-shaped, hexagon shaped, octagon-shaped, orthe like). In some embodiments, facets 716 comprise reflective surfaces(e.g., mirrors). As described above using FIG. 7A, facets 716 reflecttransmission light 715 to form transmission light 717, which may includeone or more transmission light beams for illuminating objects in a FOV714. Polygon mirror 710 is configured to rotate about an axis 712 using,for example, a motor. Therefore, each facet of polygon mirror 710 takesturn to reflect light. In the present disclosure, oscillation meanscontinuously moving back and forth in two opposite directions (e.g.,clockwise and counterclockwise) within a predetermined angular range(e.g., 40 degrees, 80 degrees, etc. degrees) in a periodical ornon-periodical manner. Rotation means continuously moving in only onedirection for at least 360 degrees. Thus, polygon mirror 710 isconfigured to rotate continuously for at least 360 degrees. As describedabove, mirror 704 may be un-moveable at all or may be configured tooscillate between two angular positions.

In some embodiments, at any particular time, multiple transmission lightbeams of light 715 can be reflected by a same facet of polygon mirror710 to form multiple transmission light beams of light 717. In someembodiments, multiple transmission light beams of light 715 arereflected by different facets of polygon mirror 710. When transmissionlight beams of light 717 travel to illuminate one or more objects in FOV720, at least a portion of transmission light beams of light 717 isreflected or scattered to form return light (not shown). The returnlight is redirected (e.g., reflected) by polygon mirror 710 to form thefirst redirected return light (not shown), which is directed towardmirror 704. The first redirected return light is redirected again (e.g.,reflected) by mirror 704 to form the second redirected return light,which is directed toward transceiver 702. In some embodiments, secondredirected return light is collected first by a collection lens (notshown). The collection lens then directs the collected return light totransceiver 702. Transceiver 702 may include a receiver to receive anddetect the return light. Thus, in some embodiments, polygon mirror 710and mirror 704 are used for both transmitting light beams to illuminateobjects in an FOV and for receiving and redirecting return light to areceiver of the LiDAR device 700. The use of polygon mirror 710 andmirror 704 for both steering transmission light out to the FOV and forsteering return light back to the receiver makes the LiDAR device morecompact.

In some embodiments, the first redirected return light is formed frommultiple transmission light beams of light 717 and is reflected by asame facet of polygon mirror 710 at any particular time. In someembodiments, the first redirected return light is reflected by differentfacets of polygon mirror 710 at any particular time. The LiDAR device700 shown in FIG. 7A is described in more detail in U.S. non-provisionalpatent application Ser. No. 16/682,774, filed on Nov. 14, 2018, entitled“LIDAR SYSTEMS THAT USE A MULTI-FACET MIRROR”, the content of which isincorporated by reference in it is entirety for all purposes.

In some embodiments, at least one of facets 716 of polygon mirror 710shown in FIG. 7B have a non-90 degree tile angle. A tilt angle is anangle between the normal direction of a facet and the rotational axis ofthe polygon mirror. Therefore, for a facet of polygon mirror 710, thetilt angle is between the direction perpendicular to a facet and itsrotational axis 712. One such tilt angle 745 is shown in FIG. 7B as theangle formed by rotational axis 712 and the normal direction 742 offacet 716B. In the example shown in FIG. 7B, the tilt angle 745 is not a90-degree angle. FIG. 7B illustrates that each facet 716A-D of polygonmirror 710 has a tilt angle that is not 90 degrees, thereby formingwedged facets. A wedged facet is not parallel to the rotational axis.For example, in FIG. 7B, facet 716B is not parallel to rotational axis712. Therefore, the wedged facet or a cross-section of polygon mirror710 may have a trapezoidal shape. It is understood that a facet of apolygon mirror can be configured to have a non-90 degree tilt angle or a90-degree tilt angle. And different facets of a polygon mirror can havethe same or different tilt angles.

FIG. 8 illustrates a top view of a rear-view mirror assembly 830 of avehicle. The rear-review mirror assembly 830 comprises a simplifiedLiDAR device 800 mounted therein. Similar to the embodiment shown inFIG. 7A, the LiDAR device 800 shown in FIG. 8 comprises transceiverarray 802, a mirror 804, and a polygon mirror 810. These components ofthe LiDAR device 800 are the same or similar to those described above,and are thus not repeatedly described. As shown in FIG. 8, dimensions oftransceiver array 802, mirror 804, and polygon mirror 810 can beconfigured such that they are enclosed in rear-view mirror assembly 830.In some embodiments, other components of the LiDAR device 800 may alsobe disposed within rear-view mirror assembly 830. It is understood thatthese components may also configured to be enclosed in another smallspace such as a light housing of a vehicle, a corner space of a vehicle,etc. In some embodiments, one or more transceivers, a polygon mirror,and a mirror (e.g., a fixed or galvanometer mirror) are enclosable intoa space having a length of about 2-6 inches, a width of about 2-6inches, and a height of about 1-4 inches.

As shown in FIG. 8, transceiver array 802, mirror 804, and polygonmirror 810 are disposed within rear-view mirror assembly 830 in a mannersuch that the LiDAR device 800 can scan a horizontal FOV of about ormore than 120 degrees. FIG. 8 shows a top view of rear-view mirrorassembly 830 (e.g., the viewing direction is perpendicular to the roadsurface and is parallel to the rear-view mirror of assembly 830). InFIG. 8, polygon mirror 810 is mounted such that its rotational axis isperpendicular to the road surface. Therefore, in the embodiment shown inFIG. 8, the polygon mirror 810, when rotating about its rotational axis,can scan transmission light beams and receive return light in thehorizontal direction of the FOV. The horizontal FOV can be about 120degrees or greater. As described below in greater detail, the facet tiltangles of polygon mirror 810 can also be arranged such that it can alsoscan transmission light beams and receive return light in the verticaldirection of the FOV. It is understood that polygon mirror 810 can beconfigured and disposed in any desired manner within rear-view mirrorassembly 830 to scan transmission light beams and receive return lightin one or both the horizontal direction and the vertical direction.

In some embodiments, the front cover of rear-view mirror assembly 830 ofa vehicle is made of infrared (IR) polycarbonate materials such thatinfrared light can be transmitted in and out of the front cover of therear-view mirror assembly 830, but lights in other wavelengths cannot.For example, the light beams of a LiDAR device may have the wavelengthof about 850 nm, about 905 nm, about 940 nm, about 1064 nm, about 1550nm, about 2000 nm, or any other infrared wavelength ranges. Therefore,these infrared light beams can be transmitted to the FOV through thefront cover of rear-view mirror assembly 830 and the return light canalso be received through the front cover. If the LiDAR device 800 ismounted in other parts of the vehicle, similar IR polycarbonatematerials can be used to allow infrared light to travel through.

FIGS. 9A-9D illustrates polygon mirror 900, 930, 960, and 990. Thesedifferent embodiments can be used to implement polygon mirror 710 and810 described above. For each of the different embodiments of polygonmirrors shown in FIGS. 9A-9D, at least two reflective facets of thepolygon mirror are arranged in the following manner. For the at leasttwo reflective facets, each facet is arranged such that a first edge, asecond edge, and a third edge of the reflective facet correspond to afirst line, a second line, and a third line; the first line and thesecond line intersect to form a first internal angle of a planecomprising the reflective facet; and the first line and the third lineintersect to form a second internal angle of the plane comprising thereflective facet. The first internal angle is an acute angle, and thesecond internal angle is an obtuse angle.

Using polygon mirror 900 as an example, polygon mirror 900 comprises atop surface 910, a bottom surface 912, and multiple facets 902, 904,906, and 908 (e.g., the four side surfaces). Facets 902, 904, 906, and908 can also be designated as a left reflective facet, a frontreflective facet, a right reflective facet, and a back reflective facet.Facets 902, 904, 906, and 908 reflect light and therefore are alsoreferred to as reflective facets. In one embodiment as illustrated bypolygon mirror 900, facets 904 and 908 (e.g., the front and back facets)are parallelogram-shaped facets and facets 902 and 906 (e.g., the leftand right facets) are rectangle-shaped facets. As shown in FIG. 9A,facet 904 comprises three edges 915, 917, and 919. These three edgescorrespond to three lines. For instances, a first line can include apart of edge 917, entire edge 917, or an extended line of edge 917(e.g., the extended straight line of edge 917). Similarly, a second linecan include a part of edge 915, entire edge 915, or an extended line ofedge 915 (e.g., the extended straight line of edge 915). And a thirdline can include a part of edge 919, entire edge 919, or an extend lineof edge 919 (e.g., the extended straight line of edge 919). The firstline (corresponding to edge 917) and the second line (corresponding toedge 915) form a first internal angle of a 2-dimensional plane thatcomprises facet 904. The first internal angle is an acute angle (e.g.,an angle that is less than 90 degrees). The first line (corresponding toedge 917) and the third line (corresponding to edge 919) form a secondinternal angle of the plane that comprises facet 904. The secondinternal angle is an obtuse angle (e.g., an angle that is greater than90 degrees but less than 180 degrees). In one embodiment, facet 904 is aparallelogram-shaped facet. Similarly, facet 908 can also be aparallelogram-shaped facet. A parallelogram-shaped facet has non-90degree internal angles. In other embodiments, facets 904 and 908 mayhave an acute internal angle and an obtuse internal angle, but may notbe parallelogram-shaped facets. For example, they may have a trapezoidalshape or any other desired shaped.

In the embodiment shown in FIG. 9A, facets 902 and 906 arerectangle-shaped facets. Thus, the internal angles of the respective2-dimensional planes comprising facets 902 and 906 are all 90-degreeangles. Because facets 904 and 908 do not have all 90-degree internalangles (e.g., they are parallelogram-shaped facets), facets 902 and 906have non-90 degree tilt angles. A tilt angle of a reflective facet is anangle between the normal direction of the reflective facet and an axisabout which the polygon mirror is rotatable. Thus, for facet 902, itstilt angle 923 is the angle formed by its normal direction 920 androtational axis 901 of polygon mirror 900. This tilt angle 923 is anon-90 degree angle (e.g., an acute angle). If tilt angle 923 is anacute angle, facet 902 is tilted such that it can direct transmissionlight toward, or receive return light from, an upper part of a verticaldirection of the FOV. Similarly, for facet 906, its tilt angle 925 isformed by its normal direction 924 and rotational axis 901 of polygonmirror 900. This tilt angle 925 is also a non-90 degree angle (e.g., anobtuse angle). If tilt angle 925 is an obtuse angle, facet 906 is tiltedsuch that it can direct transmission light toward, or receive returnlight from, a lower part of the vertical direction of the FOV.

In the embodiments of polygon mirror 900, facets 904 and 908 may not betilted. Thus, facets 904 and 908 may have 90-degree tilt angles. Thenormal directions of facets 904 and 908 are thus perpendicular to therotational axis 901 of polygon mirror 900. As such, facets 904 and 908can direct transmission light toward, or receive return light from, amiddle part of the vertical direction of the FOV. The tilt angles offacets 902, 904, 906, and 908 are therefore configured to enablescanning of the entire or a substantial portion of the verticaldirection of the FOV. In one embodiment, the vertical FOV coverage isabout or greater than 90 degrees. In the embodiment of polygon mirror900, top surface 910 and bottom surface 912 can both beparallelogram-shaped surfaces As described above, top surface 910 andbottom surface 912 are not configured to direct light and thus can benon-reflective surfaces.

Turning now to the embodiment in FIG. 9B, polygon mirror 930 comprises atop surface 940, a bottom surface 942, and multiple facets 932, 934,936, and 938 (e.g., the four side surfaces). Facets 932, 934, 936, and938 can also be designated as a left reflective facet, a frontreflective facet, a right reflective facet, and a back reflective facet.Facets 932, 934, 936, and 938 reflect light and therefore are alsoreferred to as reflective facets. For polygon mirror 930, all facets932, 934, 936 and 938 (e.g., the left, right, front, and back facets)are parallelogram-shaped facets. As shown in FIG. 9B, facet 934comprises three edges 945, 947, and 949. These three edges correspond tothree lines. For instances, a first line can include a part of edge 947,the entire edge 947, or an extended line of edge 947 (e.g., the extendedstraight line of edge 947). Similarly, a second line can include a partof edge 945, the entire edge 945, or an extended line of edge 945 (e.g.,the extended straight line of edge 945). And a third line can include apart of edge 949, the entire edge 949, or an extend line of edge 949(e.g., the extended straight line of edge 949). The first linecorresponding to edge 947 and the second line corresponding to edge 945form a first internal angle of a 2-dimensional plane that comprisesfacet 934. The first internal angle is an acute angle (e.g., an anglethat is less than 90 degrees). The first line (corresponding to edge947) and the third line (corresponding to edge 949) form a secondinternal angle of the plane that comprises facet 934. The secondinternal angle is an obtuse angle (e.g., an angle that is greater than90 degrees but less than 180 degrees). In one embodiment, facet 934 is aparallelogram-shaped facet. Similarly, facet 938 is alsoparallelogram-shaped facets. Both faces 934 and 938 (e.g., the front andback facets) have non-90 degree internal angles. In other embodiments,facets 934 and 938 may have an acute internal angle and an obtuseinternal angle, but may not be parallelogram-shaped facets. For example,they may have a trapezoidal shape or any other desired shaped.

In the embodiment shown in FIG. 9B, the internal angles of therespective 2-dimensional planes comprising facets 932 and 936 may not be90-degree angles. Similar to those described above, the internal anglesof the 2-dimensional plane comprising facets 932 and 936 may have oneobtuse angle and one acute angle. In one embodiment, facets 932 and 936may be parallelogram-shaped facets. They can have any other desiredshapes (e.g., trapezoidal shape). Because facets 934 and 938 have non-90degree internal angles (e.g., they are parallelogram-shaped facets),facets 932 and 936 have non-90 degree tilt angles. Similar to thosedescribed above with respect to facets 902 and 904 of polygon mirror900, facets 932 and 934 of polygon mirror 930 have non-90 degree tiltangles (e.g., tilt angle 953 of facet 932 is an acute angle and tiltangle 955 of facet 936 is an obtuse angle). Because of their tiltangles, facets 932 and 934 can direct transmission light toward, orreceive return light from, an upper part and a lower part, respectively,of a vertical direction of the FOV.

Similarly, because facets 932 and 936 (e.g., the left and right facets)of polygon mirror 930 have non-90 degree internal angles (e.g., they areparallelogram-shaped facets), facets 934 and 938 (e.g., the front andback facets) also have non-90 degree tilt angles (e.g., the tilt angleof facet 934 may be an obtuse angle and the tilt angle of facet 938 maybe an acute angle). As such, facets 934 and 938 can direct transmissionlight toward, or receive return light from, different portions of themiddle part of the vertical direction of the FOV. Because the tiltangles of facets 934 and 938 are different, these two facets can be usedto scan different portions of the middle parts of the vertical directionof the FOV. For example, facet 934 may be used to scan the lower middlepart and facet 938 may be used to scan the upper middle part. Scan linesobtained using facets 934 and 938 may thus be interleaved (shown asexample scan lines 1014 and 1018 in FIG. 10 below). The tilt angles offacets 932, 934, 936, and 938 are therefore configured to enablescanning of the entire or a substantial portion of the verticaldirection of the FOV. In one embodiment, the vertical FOV coverage isabout or more than 90 degrees. In the embodiment of polygon mirror 930,top surface 940 and bottom surface 942 can be both parallelogram-shapedsurfaces or rectangle-shaped surfaces. As described above, the topsurface 940 and bottom surface 942 are not configured to direct lightand thus can be non-reflective surfaces.

Turning now to the embodiment in FIG. 9C, polygon mirror 960 comprises atop surface 970, a bottom surface 972, and multiple facets 962, 964,966, and 968 (e.g., the four side surfaces). Facets 962, 964, 966, and968 can also be designated as a left reflective facet, a frontreflective facet, a right reflective facet, and a back reflective facet.Facets 962, 964, 966, and 968 reflect light and therefore are alsoreferred to as reflective facets. In one embodiment illustrated bypolygon mirror 960, facets 962 and 966 (e.g., the left and right facets)are parallelogram-shaped facets; and facets 964 and 968 (e.g., the frontand back facets) are rectangular shaped facets. Therefore, 2-dimensionalplanes comprising facets 962 and 966 have non-90 degree internal angles.And 2-dimensional planes comprising facets 964 and 968 have 90-degreeinternal angles.

In the embodiment shown in FIG. 9C, because facets 962 and 966 havenon-90 degree internal angles (e.g., they are parallelogram-shapedfacets), facets 964 and 968 (e.g., the front and back facets) havenon-90 degree tilt angles. Similar to those described above, the tiltangle of facet 968 is an acute angle and tilt angle of facet 964 is anobtuse angle). Because of their tilt angles, facets 964 and 968 candirect transmission light toward, or receive return light from, a lowerpart and an upper part, respectively, of a vertical direction of theFOV. Thus, in this embodiment, the front and back facets are used forscanning the lower and upper parts of the vertical FOV, respectively.

In the embodiments of polygon mirror 960, facets 962 and 966 may not betilted. Thus, facets 962 and 966 may have 90-degree tilt angles. Thenormal directions of facets 962 and 966 are perpendicular to therotational axis 961 of polygon mirror 900. As such, facets 962 and 966(e.g., the left and right facets) can direct transmission light toward,or receive return light from, a middle part of the vertical direction ofthe FOV. The tilt angles of facets 962, 964, 966, and 968 are thereforeconfigured to enable scanning the entire or a substantial portion of thevertical direction of the FOV. In one embodiment, the vertical FOVcoverage is about or greater than 90 degrees. In the embodiment ofpolygon mirror 960, top surface 970 and bottom surface 972 can be bothbe parallelogram-shaped surfaces or rectangle-shaped surfaces.

FIG. 9D illustrates a polygon mirror 990, which can be similar to any ofthe polygon mirror 900, 930, and 960 described above. Polygon mirror990, in addition, comprises chamfered edges. For example, edges 993 and995 of polygon mirror 990 can be rounded edges, sloped edges, bevelededges, curved edges, etc.

Polygon mirror 900, 930, 960, and 990 described above are forillustration purposes. It is understood that various characteristics(e.g., the internal angles of the facets, the tilt angles of the facets,the dimension of the facets, the shape of the facets, etc.) of thepolygon mirror can also be configured to scan an FOV according to anydesired scanning requirements (e.g., angular scanning ranges in thehorizontal and vertical directions). As one example, at least one of themultiple reflective facets of a polygon mirror can have a tilt anglethat is different from the tilt angles of the other reflective facets.As another example, each of the reflective facets of a polygon mirrormay have a tilt angle that is different from tilt angles of the otherreflective facets. As another example, two opposite reflective facets ofa polygon mirror (e.g., the front and back facets of polygon mirror 900,the left and right facets of polygon mirror 960) can have a first tiltangle; and two other opposite reflective facets can have a second tiltangle. The first tilt angle can be the same as or different from thesecond tilt angle. As another example, two opposite reflective facetsmay have different tilt angles. For instance, facets 902 and 906 (theleft and right facets) of polygon mirror 900 in FIG. 9A have differenttilt angles (one acute angle and on obtuse angle). The two oppositefacets 716B and 716D of polygon mirror 710 have the same tilt angle. Insome embodiments, the difference between the tilt angles of the multiplefacets of the polygon mirror is between about 10 degrees to +10 degrees.

FIG. 10 illustrates an example LiDAR scanning pattern 1010 using someembodiments of a polygon mirror disclosed herein, according to someembodiments. As described above, by configuring the polygon mirror tohave different characteristics (e.g., parallelogram-shaped facets,different tilt angles between facets, or the like), the polygon mirrorcan be used to scan the FOV in both the horizontal and verticaldirections when it rotates about the rotational axis. In one embodiment,the scanning of the FOV in the horizontal direction is enabled by therotation of the polygon mirror (e.g., at a speed of a few thousandsrounds per minute). In some embodiments, the polygon mirror isconfigured to scan a horizontal FOV of about or greater than 120degrees. The scanning of the FOV in the vertical direction is enabled bythe configurations of the polygon mirror including, for example, thenon-90 degree tilt angles of one or more facets.

FIG. 10 illustrates a scanning pattern 1010 obtained using polygonmirror 930 shown in FIG. 9B. As described above, for polygon mirror 930,facet 932 (e.g., the left facet) is configured to have an acute tiltangle and facet 936 is configured to have an obtuse tilt angle. Theacute tilt angle of facet 932 facilitates generating of LiDAR scan lines1012 corresponding to a first part of a vertical FOV. The first part ofthe vertical FOV in FIG. 10 can be the upper part of the vertical FOV.Facet 936 (e.g., the right facet) of polygon mirror 930 is configured tohave an obtuse tilt angle, which facilitates generating of LiDAR scanlines 1016 corresponding to a second part of a vertical FOV. The secondpart of the vertical FOV can be the lower part of the vertical FOV.Thus, in this example, the first part of the vertical FOV and the secondpart of the vertical FOV are at the two end parts of the vertical FOV.

FIG. 10 further illustrates LiDAR scan lines 1014 and 1018, which aregenerated by facets 934 and 938 (e.g., the front and back facets). Asdescribed above, facets 934 and 938 have non-90 degree tilt angles(e.g., they are not parallel to the rotational axis 901). Facets 934 and938 facilitate generating of LiDAR scan lines 1014 and 1018, whichcorrespond to the middle part of the vertical FOV. In some embodiments,the polygon mirror is configured to scan a vertical FOV of about orgreater than 90 degrees. In some embodiments, facets 934 and 938 mayhave a small tilt angle difference (e.g., within +/−2-5 degrees) suchthat they can enable generating LiDAR scan lines that corresponding to,for example, a higher middle part and a lower middle part of thevertical FOV. For instance, the tilt angles of facets 934 and 938 ofpolygon mirror 930 may be configured such that scan lines 1014 arepositioned slightly below scan lines 1018. Because facets 934 and 938have non-90 degree tilt angles, scan lines 1014 and 1018 may interleave.In some embodiments, the middle part of the vertical FOV corresponds toa region-of-interest (ROI). Therefore, by interleaving patterns 1014 and1018 (generated by two facets), the scanning resolution of the middlepart is improved for the ROI region. In some embodiments, if the titleangles of two opposing facets (e.g., facets 904 and 908 of polygonmirror 900 in FIG. 9A) have 90-degree tilt angles (e.g., the facets areparallel to the rotational axis), the scan lines obtained by the facetsmay thus overlap. It is understood that depending on the configurationof the polygon mirror, the vertical FOV can be scanned in any desiredmanner. For example, the polygon mirror facets can be configured suchthat one or more ROI regions can be scanned with higher scanningresolutions. The polygon mirror can also be configured to have anynumber of facets (e.g., four, five, six, etc.) with same or differentfacet angles. Correspondingly, the scanning pattern can be distributedin any desired manner.

FIG. 11A illustrates a top view of a rear-view mirror assembly 1110 anda horizontal field-of-view obtainable by a LiDAR device mounted in therear-view mirror assembly 1110, according to some embodiments. FIG. 11Billustrates a top view of a vehicle 1120 and the horizontal FOVs at thetwo sides of the vehicle 1120, according to some embodiments. FIG. 11Cillustrates a side view of a rear-view mirror assembly 1110 and avertical field-of-view obtainable by a LiDAR device mounted in therear-view mirror assembly, according to some embodiments. FIG. 11Dillustrates a side view of a vehicle 1120 and the vertical FOVs at aside of the vehicle 1120, according to some embodiments. FIGS. 11A-11Dillustrate that multiple LiDAR devices described above (e.g., LiDARdevice 700 and 830) can be mounted in different locations of a vehicle.

As shown in FIGS. 11A-D, a vehicle 1120 can have multiple compact LiDARdevices (not shown). The multiple LiDAR devices can be mounted to atleast two of a left side, a front side, a front side, and a back side ofvehicle 1120. For example, at least one of the multiple LiDAR devices ismounted at the left side of the vehicle, and at least one of theplurality of LiDAR devices is mounted at the right side of the vehicle.FIG. 11B illustrates this embodiment where the LiDAR devices are mountedin the left and right rear-view mirror assemblies of the vehicle 1120.In some embodiments, at least one of the multiple LiDAR devices ismounted at the front side of the vehicle, and at least one of theplurality of LiDAR devices is mounted at the back side of the vehicle.For instance, the LiDAR devices can be mounted at, integrated with, orenclosed in the front bumper, the front engine cover, the backsidebumper, front and back corners, headlight housings, rear light housings,etc. of the vehicle 1120. Each of the multiple LiDAR devices maycomprise a mirror (e.g., an un-moveable mirror or a galvanometer mirror)and a polygon mirror. The polygon mirror may have multiple facetsconfigured as described above.

As shown in FIGS. 11A-11D, by mounting multiple compact LiDAR devices indifferent locations of the vehicle, an ultra-wide FOV can be achieved.For example, on each side of the vehicle (e.g., left side and rightside), a horizontal FOV of about 120 degrees (or greater) and a verticalFOV of about 90 degrees (or greater) can be achieved. Thus, if two LiDARdevices are used as shown in FIG. 11B, the horizontal FOV can be about240 degrees (or greater). Furthermore, by mounting multiple compactLiDAR devices at different locations, the number of blind spots of thevehicle can be significantly reduced or eliminated. In some embodiment,when multiple compact LiDAR devices are mounted on a vehicle, each ofthem is independently operable from other LiDAR devices. For example,depending on the requirements (e.g., from the vehicle), the LiDARdevices mounted at different locations of the vehicle may be turned on,turned off, instructed to scan an ROI area, instructed to reduce thescan resolution, etc. Independently controlling the LiDAR devices canfacilitate reducing energy consumption and improve energy efficiency.

FIG. 12 is a flowchart illustrating a method 1200 for scanning afield-of-view using a light detection and ranging (LiDAR) device. TheLiDAR device comprises a polygon mirror having a plurality of reflectivefacets. Method 1200 can begin with any of the steps 1202, 1206, and1210. In step 1202, a first reflective facet of the plurality ofreflective facets of the polygon mirror steers light to scan a firstpart of the field-of-view in a vertical direction. The first reflectivefacet is associated with an acute tilt angle. The first reflective facetcan be, for example, facet 902 of polygon mirror 900 or facet 932 ofpolygon mirror 930 (FIGS. 9A and 9B). Step 1204 generates scan lines(e.g., scan lines 1012 in FIG. 10) corresponding to the first part ofthe field-of-view in the vertical direction. The first part of the FOVmay be an upper part of the FOV in the vertical direction.

In step 1206, a second reflective facet of the plurality of reflectivefacets of the polygon mirror steers light to scan a second part of thefield-of-view in a vertical direction. The second reflective facet isassociated with an obtuse tilt angle. The second reflective facet canbe, for example, facet 906 of polygon mirror 900 or facet 936 of polygonmirror 930 (FIGS. 9A and 9B). Step 1208 generates scan lines (e.g., scanlines 1016 in FIG. 10) corresponding to the second part of thefield-of-view in the vertical direction. The second part of the FOV maybe a lower part of the FOV in the vertical direction. In someembodiments, the first part of the field-of-view and the second part ofthe field-of-view are at the two ends of the vertical field-of-view.

In step 1210, one or more additional reflective facets of the polygonmirror steer light to scan one or more additional parts of thefield-of-view in the vertical direction. The one or more additionalfacets can be, for example, facets 904 and 908 of polygon mirror 900; orfacets 934 and 938 of polygon mirror 930. Step 1212 generates scan lines(e.g., scan lines 1014 and 1018) in FIG. 10) corresponding to the one ormore additional parts of the FOV in the vertical direction.

In some embodiments, step 1210 can include two parts. In the first partof step 1210, a third reflective facet of the plurality of reflectivefacets of the polygon mirror steers light to scan a third part of thefield-of-view in a vertical direction. In the second part of step 1210,a fourth reflective facet of the plurality of reflective facets of thepolygon mirror steers light to also scan the third part of thefield-of-view in a vertical direction. Thus, the scan lines obtained bythe third and fourth reflective facets may overlap.

In some embodiments, in the second part of step 1210, the fourthreflective facet of the plurality of reflective facets of the polygonmirror steers light to scan a fourth part of the field-of-view in avertical direction. The fourth part of the FOV is a different part fromthe third part. As a result, the scan lines corresponding to the thirdand fourth parts of the field-of-view are interleaved.

In some embodiments, step 1212 comprises generating scan lines (e.g.,scan lines 1014 and 1018 shown in FIG. 10) corresponding a middle partof the field-of-view in the vertical direction. It is understood thatsteps of method 1200 can be arranged in any order, removed, added,omitted, and/or repeated in any desired manner.

The foregoing specification is to be understood as being in everyrespect illustrative and exemplary, but not restrictive, and the scopeof the invention disclosed herein is not to be determined from thespecification, but rather from the claims as interpreted according tothe full breadth permitted by the patent laws. It is to be understoodthat the embodiments shown and described herein are only illustrative ofthe principles of the present invention and that various modificationsmay be implemented by those skilled in the art without departing fromthe scope and spirit of the invention. Those skilled in the art couldimplement various other feature combinations without departing from thescope and spirit of the invention.

What is claimed is:
 1. A light detection and ranging (LiDAR) scanningdevice, comprising: a first mirror disposed to receive one or more lightbeams; a polygon mirror optically coupled to the first mirror, whereinthe polygon mirror comprises a plurality of reflective facets, whereinfor at least two of the plurality of reflective facets, each reflectivefacet is arranged such that: a first edge, a second edge, and a thirdedge of the reflective facet correspond to a first line, a second line,and a third line, the first line and the second line intersect to form afirst internal angle of a plane comprising the reflective facet, thefirst internal angle being an acute angle, the first line and the thirdline intersect to form a second internal angle of the plane comprisingthe reflective facet, the second internal angle being an obtuse angle;wherein the combination of the first mirror and the polygon mirror, whenat least the polygon mirror is rotating, is configured to: steer the oneor more light beams both vertically and horizontally to illuminate anobject within a field-of-view, obtain return light formed based on thesteered one or more light beams illuminating the object within thefield-of-view, and redirect the return light to an optical receiverdisposed in the LiDAR scanning system.
 2. The device of claim 1, whereinthe first mirror is an un-moveable mirror redirecting the one or morelight beams to the polygon mirror.
 3. The device of claim 1, wherein thefirst mirror is a galvanometer mirror controllable to oscillate about anaxis of the first mirror.
 4. The device of claim 1, wherein the polygonmirror comprises four, five, or six reflective facets.
 5. The device ofclaim 1, wherein at least two reflective facets of the polygon mirrorare parallelogram-shaped facets.
 6. The device of claim 1, wherein allreflective facets of the polygon mirror are parallelogram-shaped facets.7. The device of claim 1, wherein the polygon mirror comprises a topnon-reflective surface, a bottom non-reflective surface, a leftreflective facet, a right reflective facet, a front reflective facet,and a back reflective facet.
 8. The device of claim 7, wherein the topnon-reflective surface and the bottom non-reflective surface arerectangle-shaped surfaces, and wherein the left reflective facet, theright reflective facet, the front reflective facet, and the backreflective facet are parallelogram-shaped facets.
 9. The device of claim7, wherein the front reflective facet and the back reflective facet arerectangle-shaped, and wherein the left reflective facet and the rightreflective facet are parallelogram-shaped facets, and the topnon-reflective surface and the bottom non-reflective surface areparallelogram-shaped surfaces.
 10. The device of claim 7, wherein theleft reflective facet and the right reflective facet arerectangle-shaped facets, and wherein the front reflective facet, theback reflective facet, the top non-reflective surface, and the bottomnon-reflective surface are parallelogram-shaped facets.
 11. The deviceof claim 1, wherein at least one of the plurality of reflective facetsis associated with a tilt angle that is different from tilt angles ofthe other reflective facets, the tilt angles of reflective facets beingrespective angles between normal directions of the respective reflectivefacets and an axis about which the polygon mirror is rotatable.
 12. Thedevice of claim 11, wherein each of the reflective facets is associatedwith a tilt angle that is different from tilt angles of the otherreflective facets.
 13. The device of claim 11, wherein: two oppositereflective facets are associated with a first tilt angle; two otheropposite reflective facets are associated with a second tilt angle, thefirst tilt angle being different from the second tilt angle.
 14. Thedevice of claim 11, wherein two opposite reflective facets areassociated with different tilt angles.
 15. The device of claim 11,wherein a difference of the tilt angles is between about −10 degrees to+10 degrees.
 16. The device of claim 1, wherein the field-of-viewcomprises a horizontal field-of-view of about or greater than 120degrees and a vertical field-of-view of about or greater than 90degrees.
 17. The device of claim 1, wherein a first reflective facetassociated with an acute tilt angle facilitates generating of LiDAR scanlines corresponding to a first part of a vertical field-of-view; andwherein a second reflective facet associated with an obtuse tilt anglefacilitates generating of LiDAR scan lines corresponding to a secondpart of a vertical field-of-view; the first part of the verticalfield-of-view and the second part of the vertical field-of-view being atthe two ends of the vertical field-of-view.
 18. The device of claim 1,wherein the combination of the polygon mirror and the first mirror areenclosed in at least one of a rear-view mirror assembly or a lighthousing of a vehicle.
 19. A light detection and ranging (LiDAR) scanningsystem, comprising: a plurality of LiDAR devices mountable to at leasttwo of a left side, a front side, a front side, and a back side of avehicle, wherein each of the plurality of LiDAR devices comprises: afirst mirror disposed to receive one or more light beams; and a polygonmirror optically coupled to the first mirror, wherein the polygon mirrorcomprises a plurality of reflective facets, wherein for at least two ofthe plurality of reflective facets, each reflective facet is arrangedsuch that: a first edge, a second edge, and a third edge of thereflective facet corresponding to a first line, a second line, and athird line; the first line and the second line intersect to form a firstinternal angle of a plane comprising the reflective facet, the firstinternal angle of the reflective facet being an acute angle; and thefirst line and the third line intersect to form a second internal angleof a plane comprising the reflective facet, the second internal angle ofthe respective plane being an obtuse angle.
 20. The system of claim 19,wherein at least one of the plurality of LiDAR devices is mounted at theleft side of the vehicle, and wherein at least one of the plurality ofLiDAR devices is mounted at the right side of the vehicle.
 21. Thesystem of claim 19, wherein at least one of the plurality of LiDARdevices is mounted at the front side of the vehicle, and wherein atleast one of the plurality of LiDAR devices is mounted at the back sideof the vehicle.
 22. The system of claim 19, wherein at least one of theplurality of LiDAR devices is enclosed in at least one of a rear-viewmirror assembly or a light housing of the vehicle.
 23. The system ofclaim 19, wherein the plurality of LiDAR devices comprises: a firstLiDAR device enclosed in a first rear-view mirror assembly of thevehicle, and a second LiDAR device enclosed in a second rear-view mirrorassembly of the vehicle.
 24. A vehicle comprising a light detection andranging (LiDAR) scanning system, the system comprising: a plurality ofLiDAR devices mountable to at least two of a left side, a front side, afront side, and a back side of a vehicle, wherein each of the pluralityof LiDAR devices comprises: a first mirror disposed to receive one ormore light beams; and a polygon mirror optically coupled to the firstmirror, wherein the polygon mirror comprises a plurality of reflectivefacets, wherein for at least two of the plurality of reflective facets,each reflective facet is arranged such that: a first edge, a secondedge, and a third edge of the reflective facet corresponding to a firstline, a second line, and a third line; the first line and the secondline intersect to form a first internal angle of a plane comprising thereflective facet, the first internal angle of the reflective facet beingan acute angle; and the first line and the third line intersect to forma second internal angle of a plane comprising the reflective facet, thesecond internal angle of the respective plane being an obtuse angle. 25.A method for scanning a field-of-view using a light detection andranging (LiDAR) device, the LiDAR device comprises a polygon mirrorhaving a plurality of reflective facets, the method comprising:steering, by a first reflective facet of the plurality of reflectivefacets of the polygon mirror, light to scan a first part of thefield-of-view in a vertical direction, wherein the first reflectivefacet is associated with an acute tilt angle; steering, by a secondreflective facet of the plurality of reflective facets of the polygonmirror, light to scan a second part of the field-of-view in the verticaldirection, wherein the second reflective facet is associated with anobtuse tilt angle; generating scan lines corresponding to the first partof the field-of-view in the vertical direction; and generating scanlines corresponding to the second part of the field-of-view in thevertical direction.
 26. The method of claim 25, wherein the first partof the field-of-view and the second part of the field-of-view are at thetwo ends of the vertical field-of-view.
 27. The method of claim 25,further comprising: steering, by one or more additional reflectivefacets of the polygon mirror, light to scan one or more additional partsof the field-of-view in the vertical direction; and generating scanlines corresponding to the one or more additional parts of the FOV inthe vertical direction.
 28. The method of claim 27, wherein steeringlight to scan one or more additional parts of the field-of-view in thevertical direction comprises: steering, by a third reflective facet ofthe plurality of reflective facets of the polygon mirror, light to scana third part of the field-of-view in a vertical direction; steering, bya fourth reflective facet of the plurality of reflective facets of thepolygon mirror, the third part of the field-of-view in a verticaldirection.
 29. The method of claim 27, wherein steering light to scanone or more additional parts of the field-of-view in the verticaldirection comprises: steering, by a third reflective facet of theplurality of reflective facets of the polygon mirror, light to scan athird part of the field-of-view in a vertical direction; steering, by afourth reflective facet of the plurality of reflective facets of thepolygon mirror, a fourth part of the field-of-view in a verticaldirection, wherein the scan lines corresponding to the third and fourthparts of the field-of-view are interleaved.
 30. The method of claim 27,wherein generating scan lines corresponding to the one or moreadditional parts of the field-of-view in the vertical directioncomprises generating scan lines corresponding a middle part of thefield-of-view in the vertical direction.